Papers - YOKOTA Kenji
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Decreasing phosphorous sorption using fishpond sediment and goat manure in acid upland soil Reviewed International coauthorship International journal
Arief Hartono, Syaiful Anwar, Avilia Triani Putri, Kenji Yokota
Journal of ISSAAS (International Society for Southeast Asian Agricultural Sciences) 24 ( 1 ) 118 - 126 2018
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
Fishpond sediment and fishpond water at Petir village, Darmaga, Bogor, Indonesia have the potential as a soil ameliorant due to the nutrient content needed by crops. This present research sought to evaluate the phosphorus (P) sorption characteristics on acid soil Typic Hapludults Darmaga treated with fishpond sediment, fishpond water, goat manure and their combination, as well as conventional fertilizers. The research was conducted from March to August 2015. The treated soil samples were incubated for 1 week and 2 weeks under room temperature. The experimental design was completely randomized design with three replications. After 1 week or 2 weeks of incubation, soil samples from treatments were subjected to P sorption experiment. The data were simulated by Langmuir and Freundlich equations, wherein data was better simulated by the Freundlich equation. The Freundlich P sorption capacity (KF) value from the combined fishpond sediment and goat manure treatment was the lowest after 1 week and 2 weeks of incubation. This treatment had a significantly higher n value than that of control after 1 week of incubation, however after 2 weeks incubation, the n value was not significantly different from the other treatments. From the KF and n values of Freundlich equation, it was suggested that a combination of fishpond sediment and goat manure was the best treatment needed to decrease P sorption capacity. The decrease of P sorption capacity should decrease the rate of P fertilizer applied by farmers.
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Changes in some soil chemical properties and production of sweet potato, Ipomoea batatas (L.) Lam, treated with fishpond sediment and water in Petir village, Darmaga, Bogor, Indonesia Reviewed International coauthorship
Arief Hartono, Kenji Yokota, Tadashi Baba, Bambang Subroto
Journal of International Society for Southeast Asian Agricultural Sciences 22 ( 2 ) 1 - 9 2016.12
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Bogor is situated about 70 km south of Jakarta, Indonesia. Bogor is situated upstream of the rivers via Jakarta. The water from Salak mountain is used by farmers not only for agriculture but also for fresh water fishponds. The study sought to clarify the nutrient content of fishpond sediment and fishpond water, evaluate their effects on soil chemical properties and determine the production of sweet potato in Petir village, Darmaga, Bogor in September 2013. Fishpond sediment and fishpond water were analyzed for selected chemical properties. The treatments in the field experiment were without any fertilizer, fishpond sediment, fishpond water, combination of fishpond sediment and fishpond water, and conventional fertilizer, arranged in completely randomized design with three replications. After 2 weeks of incubation and before planting sweet potato, the soil samples of each plot were collected and analyzed. Sweet potato were harvested after four months. The results showed that the fishpond sediment contained high levels of total nitrogen and available phosphorus, and very high organic carbon and basic cations (Ca, Mg, K and Na). The fishpond water contained relatively high total inorganic nitrogen and phosphate. From the field experiment, fishpond sediment and fishpond water improved some soil chemical properties better compared to conventional fertilizer. The combination of fishpond sediment and fishpond water was the best treatment as it resulted in the highest sweet potato yield. The results suggested that a combination of fishpond sediment and fishpond water can be recommended as soil ameliorant or fertilizer for sweet potato production.
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Promiscuous DSF production and responsiveness of the Xylella fastidiosa Rpf system Reviewed
Michael Ionescu, Kenji Yokota, Elena Antonova, Angelica Garcia, Ellen Beaulieu, Anthony T. Iavarone, Steven E. Lindow
mBio IF:6.975 7 ( 4 ) 2016.07
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Cell density-dependent regulation of gene expression in Xylella fastidiosa that is crucial to its switching between plant hosts and insect vectors is dependent on RpfF and its production of 2-enoic acids known as diffusible signal factor (DSF). We show that X. fastidiosa produces a particularly large variety of similar, relatively long-chain-length 2-enoic acids that are active in modulating gene expression. Both X. fastidiosa itself and a Pantoea agglomerans surrogate host harboring X. fastidiosa RpfF (XfRpfF) is capable of producing a variety of both saturated and unsaturated free fatty acids. However, only 2-cis unsaturated acids were found to be biologically active in X. fastidiosa X. fastidiosa produces, and is particularly responsive to, a novel DSF species, 2-cis-hexadecanoic acid that we term XfDSF2. It is also responsive to other, even longer 2-enoic acids to which other taxa such as Xanthomonas campestris are unresponsive. The 2-enoic acids that are produced by X. fastidiosa are strongly affected by the cellular growth environment, with XfDSF2 not detected in culture media in which 2-tetradecenoic acid (XfDSF1) had previously been found. X. fastidiosa is responsive to much lower concentrations of XfDSF2 than XfDSF1. Apparently competitive interactions can occur between various saturated and unsaturated fatty acids that block the function of those agonistic 2-enoic fatty acids. By altering the particular 2-enoic acids produced and the relative balance of free enoic and saturated fatty acids, X. fastidiosa might modulate the extent of DSF-mediated quorum sensing.
Importance: X. fastidiosa, having a complicated lifestyle in which it moves and multiplies within plants but also must be vectored by insects, utilizes DSF-based quorum sensing to partition the expression of traits needed for these two processes within different cells in this population based on local cellular density. The finding that it can produce a variety of DSF species in a strongly environmentally context-dependent manner provides insight into how it coordinates the many genes under the control of DSF signaling to successfully associate with its two hosts. Since the new DSF variant XfDSF2 described here is much more active than the previously recognized DSF species, it should contribute to plant disease control, given that the susceptibility of plants can be greatly reduced by artificially elevating the levels of DSF in plants, creating "pathogen confusion," resulting in lower virulence. -
Impact of antimicrobial lipopeptides from Bacillus sp. in suppression of Fusarium yellows of tatsoi Reviewed
Kenji Yokota, Hiroshige Hayakawa
Microbes and Environments IF:2.231 30 ( 3 ) 281 - 283 2015.09
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Iturin A and surfactin are antimicrobial lipopeptides produced by antagonistic Bacillus spp. We herein demonstrated that both lipopeptides amended the soil-mediated suppression of the soil-borne disease, Fusarium yellows of tatsoi (Brassica rapa var. rosularis). Significant disease suppression was conferred by the amendments of purified iturin A or surfactin to soil. However, an excess amount of iturin A or surfactin to soil resulted in the loss of disease suppression activity.。
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Characterization of possible bacterial biocontrol agents, isolated from various plants in Indonesia, against bacterial wilt and damping-off of tomato Reviewed International coauthorship
Yuliar, Koki Toyota, Kenji Yokota
Soil Microorganisms 69 ( 1 ) 39 - 47 2015.04
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
One hundred bacterial strains isolated from various plants grown organically in Indonesia were assessed for their potential biocontrol ability. Phylogenic analysis based on the 16S rRNA analysis showed that Gram positive and negative bacteria were distributed in the host plants. About 43% of them belonged to Bacillus spp. and the other genera were Achromobacter, Acinetobacter, Agrobacterium, Alcaligenes, Brevibacterium, Enterobacter, Leucobacter, Microbacterium, Paenibacillus, Pseudomonas, Serratia, and Stenotrophomonas. The screening results showed that strains EB13, EB45, and EB53 isolated from Brassica chinensis, Fragaria vesca, and Ipomea aquatica, which were identified as B. amyloliquefaciens, B. cereus, and Alcaligenes sp., increased the survivability of tomato in bacterial wilt (BWT) significantly (P<0.05) by 67%, 83%, and 72%, respectively. Two strains, EB13 and EB45, also increased the survivability of tomato in damping-off significantly (P<0.05) by 45%, while EB53 and EB87 identified as Enterobacter gergoviae showed 23% and 34% disease suppression, respectively, although the differences were not significant. EB13rifkan, EB53rif and EB87rif, spontaneous antibiotics mutants of the parent strains, were confirmed to colonize tomato roots and suppress the population of Rhizoctonia solani in soil and root A seven-day culture broth of strains EB13 and EB87 and its butanol extract showed antibiosis to R. solani and R. solanacearum. HPLC analysis revealed the productions of iturin and surfactin by EB13 and an iturin-like compound by EB87. These results indicate that plant-derived bacteria not only offer potential biocontrol agents for the two tomato diseases but also provide a new source for antibiotics iturin and surfactin.
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The hygroscopic biosurfactant syringafactin produced by Pseudomonas syringae enhances fitness on leaf surfaces during fluctuating humidity Reviewed
Adrien Burch, Viktoria Zeisler, Kenji Yokota, Lukas Schreiber, Steven Lindow
Environmental Microbiology IF:5.756 16 ( 7 ) 2086 - 2098 2014.07
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Biosurfactant production by bacteria on leaf surfaces is poorly documented, and its role in this habitat has not been explored. Therefore, we investigated the production and fitness benefits of syringafactin by Pseudomonas syringae pv. syringae B728a on leaves. Syringafactin largely adsorbed to the waxy leaf cuticle both when topically applied and when produced by cells on plants. Syringafactin increased the rate of diffusion of water across isolated cuticles and attracted water to hydrophobic surfaces exposed to high relative humidity due to its hygroscopic properties. While a wild-type and syringafactin mutant exhibited similar fitness on bean leaves incubated in static conditions, the fitness of the wild-type strain was higher under fluctuating humidity conditions typical of field conditions. When co-inoculated onto either the host plant bean or the non-host plant romaine lettuce, the proportion of viable wild-type cells recovered from plants relative to that of a mutant unable to produce syringafactin increased 10% over 10 days. The number of disease lesions incited by the wild-type strain on bean was also significantly higher than that of the syringafactin mutant. The production of hygroscopic biosurfactants on waxy leaf surfaces apparently benefits bacteria by both attracting moisture and facilitating access to nutrients.
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Agriculture and Water Use in Rural Areas as a Source of Water Pollution in Java -The Case of Petir Village, Bogor Regency, Indonesia- Reviewed
Rie Miyaura, Maki Hayashida, Kenji Yokota
Journal of Agriculture Science, Tokyo University of Agriculture 59 ( 1 ) 52 - 62 2014.06
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
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Diffusible Signal Factor (DSF) Synthase RpfF of Xylella fastidiosa Is a Multifunction Protein Also Required for Response to DSF Reviewed
Michael Ionescu, Clelia Baccari, Aline da Silva, Angelica Garcia, Kenji Yokota, Steven Lindow
Journal of Bacteriology IF:3.194 195 ( 23 ) 5273 - 5284 2013.12
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Xylella fastidiosa, like related Xanthomonas species, employs an Rpf cell-cell communication system consisting of a diffusible signal factor (DSF) synthase, RpfF, and a DSF sensor, RpfC, to coordinate expression of virulence genes. While phenotypes of a ΔrpfF strain in Xanthomonas campestris could be complemented by its own DSF, the DSF produced by X. fastidiosa (XfDSF) did not restore expression of the XfDSF-dependent genes hxfA and hxfB to a ΔrpfF strain of X. fastidiosa, suggesting that RpfF is involved in XfDSF sensing or XfDSF-dependent signaling. To test this conjecture, rpfC and rpfF of X. campestris were replaced by those of X. fastidiosa, and the contribution of each gene to the induction of a X. campestris DSF-dependent gene was assessed. As in X. fastidiosa, XfDSF-dependent signaling required both X. fastidiosa proteins RpfF and RpfC. RpfF repressed RpfC signaling activity, which in turn was derepressed by XfDSF. A mutated X. fastidiosa RpfF protein with two substitutions of glutamate to alanine in its active site was incapable of XfDSF production yet enabled a response to XfDSF, indicating that XfDSF production and the response to XfDSF are two separate functions in which RpfF is involved. This mutant was also hypervirulent to grape, demonstrating the antivirulence effects of XfDSF itself in X. fastidiosa. The Rpf system of X. fastidiosa is thus a novel example of a quorum-sensing signal synthase that is also involved in the response to the signal molecule that it synthesizes.
DOI： https://doi.org/10.1128%2FJB.00713-13
Other Link： http://jb.asm.org/content/195/23/5273.abstract
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Selecting a Research Site for Regional Agricultural Development Model -A Case of Promoting Local Products in Rural Areas of Bogor, Indonesia- Reviewed
Rie Miyaura, Hiroki Inaizumi, Akimi Fujimoto, Kenji Yokota, Hironobu Shiwachi, Tadashi Baba
Journal of Agriculture Science, Tokyo University of Agriculture 58 ( 3 ) 170 - 179 2013.12
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
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Characterization of a Diffusible Signaling Factor from Xylella fastidiosa Reviewed
Ellen D Beaulieu, Michael Ionescu, Subhadeep Chatterjee, Kenji Yokota, Dirk Trauner, Steven E Lindow
mBio IF:5.311 4 ( 1 ) 2013.01
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Cell-cell signaling in Xylella fastidiosa has been implicated in the coordination of traits enabling colonization in plant hosts as well as insect vectors. This cell density-dependent signaling has been attributed to a diffusible signaling factor (DSF) produced by the DSF synthase RpfF. DSF produced by related bacterial species are unsaturated fatty acids, but that of X. fastidiosa was thought to be different from those of other taxa. We describe here the isolation and characterization of an X. fastidiosa DSF (XfDSF) as 2(Z)-tetradecenoic acid. This compound was isolated both from recombinant Erwinia herbicola expressing X. fastidiosa rpfF and from an X. fastidiosa rpfC deletion mutant that overproduces DSF. Since an rpfF mutant is impaired in biofilm formation and underexpresses the hemagglutinin-like protein-encoding genes hxfA and hxfB, we demonstrate that these traits can be restored by ca. 0.5 µM XfDSF but not by myristic acid, the fully saturated tetradecenoic acid. A phoA-based X. fastidiosa biosensor that assesses DSF-dependent expression of hxfA or hxfB revealed a high level of molecular specificity of DSF signaling.
Importance: X. fastidiosa causes diseases in many important plants, including grape, where it incites Pierce's disease. Virulence of X. fastidiosa for grape is coordinated by cell-cell signaling molecules, designated DSF (Diffusible Signaling Factor). Mutants blocked in DSF production are hypervirulent for grape, suggesting that virulence is suppressed upon DSF accumulation and that disease could be controlled by artificial elevation of the DSF level in plants. In this work, we describe the isolation of the DSF produced by X. fastidiosa and the verification of its biological activity as an antivirulence factor. We also have developed X. fastidiosa DSF biosensors to evaluate the specificity of cell-cell signaling to be investigated.DOI： https://doi.org/10.1128/mBio.00539-12
Other Link： http://mbio.asm.org/content/4/1/e00539-12.full.pdf+html
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Comparative study on sample preparation methods for the HPLC quantification of iturin from culture supernatant of an antagonistic Bacillus strain Reviewed
Kenji Yokota, Maiko Yatsuda, Eitaro Miwa, Kyoko Higuchi
Journal of International Society for Southeast Asian Agricultural Sciences 18 ( 1 ) 70 - 75 2012.06
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Iturin is one of the antimicrobial cyclic lipopeptides produced by antagonistic strains of Bacillus
spp. This study evaluated sample preparation methods for high-performance liquid chromatography
(HPLC) quantification of iturin from culture supernatant of an iturin-producing Bacillus strain. The
acid precipitation and methanol extraction (APME) method showed a lower efficiency than the
butanol extraction and methanol substitution (BEMS) method. Direct application of culture
supernatant to HPLC analysis showed the lowest efficiency. The BEMS method was the most
effective method for quantifying the amount of iturin from culture supernatant based on the percent
recovery and the time required to perform the analysis. -
Effect of inorganic ions on bud cell formation by Fusarium oxysporum in potato dextrose broth Reviewed
Kenji Yokota, Takuma Teraoka, Hirofumi Suzuki, Keiichi Murakami, Eitaro Miwa, Kyoko Higuchi
Journal of General Plant Pathology IF:0.687 76 ( 3 ) 331 - 335 2010.10
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Potato dextrose broth (PDB), a well-known medium for cultivation of fungi, can be made from potato extract and glucose (handmade PDB) or bought as a commercial powder (commercial PDB). Previously, we reported that bud cell formation and fungal biomass of Fusarium oxysporum in handmade PDB are higher than in commercial PDB, and the presence of high molecular weight (>20 MDa) carbohydrates in PDB promoted bud cell formation by most strains of F. oxysporum. In this study, we report the effects of inorganic ions in PDB on bud cell formation and fungal biomass production by F. oxysporum. Concentrations of Mg, K, Fe, PO4 3− and SO4 2− were higher and of Na and Cl− were lower in handmade PDB than in commercial PDB. Adding each inorganic ion alone to commercial PDB showed that Mg is critical for enhancement of bud cell formation by some strains of F. oxysporum. The addition of Mg2+ with raw potato starch to commercial PDB promoted bud cell formation by some, but not all, of the seven F. oxysporum strains tested in this study.
DOI： https://doi.org/10.1007/s10327-010-0256-z
Other Link： http://link.springer.com/article/10.1007%2Fs10327-010-0256-z
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Effect of high molecular weight carbohydrates on bud cells formation by Fusarium oxysporum in potato dextrose broth Reviewed
Kenji Yokota, Takuma Teraoka, Yoshimasa Tsujii, Hirofumi Suzuki, Keiichi Murakami, Eitaro Miwa, Kyoko Higuchi
Journal of General Plant Pathology IF:0.687 76 ( 3 ) 219 - 224 2010.06
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Potato dextrose broth (PDB), one of the most popular culture media for fungi, can be made in the laboratory from potato extract and glucose (handmade PDB) and also bought as powder (commercial PDB). We compared growth of Fusarium oxysporum in handmade and commercial PDBs. For seven strains tested, bud cell formation and fungal biomass were higher in handmade PDB than in commercial PDB. Gel filtration analyses revealed that handmade PDB contained carbohydrates with molecular weights >20 MDa, while most carbohydrates in commercial PDB were <45 kDa. Freshly prepared, raw potato starch had a molecular weight >20 MDa and enhanced bud cell formation by five of seven strains when added to commercial PDB. The addition of glucose to commercial PDB promoted biomass production but not bud cell formation. Furthermore, in a semisynthetic medium containing raw potato starch, bud cell formation was enhanced for all strains tested. These results indicate that the high molecular carbohydrates present in raw potatoes enhanced bud cell formation by Fusarium oxysporum.
DOI： https://doi.org/10.1007/s10327-010-0238-1
Other Link： http://link.springer.com/article/10.1007%2Fs10327-010-0238-1
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Biocontrol of yellow disease of Brassica campestris caused by Fusarium oxysporum with Trichoderma viride under field conditions Reviewed
Ryota Kataoka, Kenji Yokota, Itsuo Goto
Archives of Phytopathology and Plant Protection 43 ( 9 ) 900 - 909 2010.06
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Trichoderma viride was selected from three species of Trichoderma and was applied to the soil for biocontrol of yellow disease of Brassica campestris caused by Fusarium oxysporum. The population density of F. oxysporum averaged 103 to 104 cfu/g of soil in eight greenhouses. Moreover, the results of application of T. viride showed that the yellow disease of the first, second, and third crops in greenhouse A was 33%, 48%, and 35% in control plot, while it was 1.4%, 11.5%, and 3.0% in T. viride plots, respectively. Also in greenhouse B, the yellow disease of the first crop was inhibited by T. viride compared with control. However, the suppressive effect of T. viride declined on the second crop. Therefore, the third crop was not cultured in greenhouse B. The population density of T. viride in greenhouse A, in which yellow disease was successfully controlled, was higher than that in greenhouse B.
DOI： https://doi.org/10.1080/03235400802075583
Other Link： http://www.tandfonline.com/doi/pdf/10.1080/03235400802075583
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Differentiation of Iturin A Productivity by the Combination of Bacillus subtilis NB22 with organic matter Reviewed
Kenji Yokota, Shizuka Hirai, Nobuhiro Kondo
Journal of International Society for Southeast Asian Agricultural Sciences 13 ( 3 ) 91 - 95 2008.04
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Bacillus subtilis NB22 (NB22) is an Iturin A producing bacteria isolated from compost. Iturin A and its related compounds show antifungal activity for several plant pathogens. In this study, Iturin A productivity was estimated by NB22 on 5 organic matters, soybean cake, soybean curd residue, wheat bran, rapeseed cake, and spent grain and hop. NB22 grew from an initial concentration of 10 sup 7 to approximately 10 sup 10 cfu/g FW in 5 days on 4 kinds of organic matters without spent grain and hop. On the other hand, Iturin A productivity of soybean cake culture was two times higher than the others. The data showed that the selection of organic matter as solid state media for Bacillus spp. was one of the critical points for the productivity of Iturin A.
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Ensuring Sufficient Yeild and High-Palatability Rice Cultivated through the Direct Sowing with Recycled-Paper Mulch in Japan Reviewed
Mayuko Okabe, Tadashi Baba, Masahiro Kamei, Kenji Yokota, Kazuo Suyama
Journal of International Society for Southeast Asian Agricultural Sciences 13 ( 3 ) 62 - 68 2008.04
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Direct sowing with recycled-paper mulch has the constraint of an unstable seedling emergence, but has the possibility of substantial labor saving in organic rice cultivation. Direct sowing with recycled-paper mulch was conducted towards overcoming its defects using cultivar Koshihikari. The percentage of emergence was higher than 70%, and that of established hills was lower than 15% because of bird damage after emergence in 2005. In 2006, an early sowing date was effective for recovering the percentage of established hills up to 76% without the use of many strings as barriers against birds. Yield had a 19% reduction as compared with conventional cultivation in 2006. The rice cultivated using paper mulch had low palatability because the protein content was 1% higher than the commonly cultivated rice in 2005, presumably resulting from the excess absorption of nitrogen supplied from the mulch paper. High palatability rice was obtained through the reduction of nitrogen application as a single basal dressing of organic fertilizer. Since the percentage of established hills highly depends on the conditions of each plot, the evaluation of adaptability for direct sowing was required for each paddy field to ensure sufficient yield.
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Identification of serine138 residue in the 4-residue segment K135K1361137S138 of LukS-I component of Staphylococcus intermedius leukocidin crucial for the LukS-I-specific function of staphylococcal leukocidin Reviewed
Akihito Nishiyama, Marie Antonette Ruth V Guerra, Noriko Sugawara, Kenji Yokota, Jun Kaneko, Yoshiyuki Kamio
Bioscience, Biotechnology, and Biochemistry 66 ( 2 ) 328 - 335 2002.02
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Luk-I produced by Staphylococcus intermedius was found to be a new member of the staphylococcal bi-component pore-forming toxin family, in which staphylococcal leukocidin, Panton-Valentine leukocidin, and gamma-hemolysin are included. Luk-I consists of LukS-I and LukF-I. From the deduced amino acid sequence of LukS-I, a 4-residue sequence, K135K1361137S138, at the root of the stem region was found to be identical with that of the phosphorylated segment of a protein phosphorylated by protein kinase A. A mutant of LukS-I (MLSI-SA), in which the Ser138 residue was replaced by an alanine residue, was created, purified, and assayed for its leukocytolytic and pore-forming activities with LukF-I. Both LukS-I and MLSI-SA formed a ring-shaped complex with LukF-I on rabbit erythrocytes and human polymorphonuclear leukocytes (HPMNLs) membrane. However, MLSI-SA showed no leukocytolytic activity with LukF-I. LukS-I was phosphorylated by protein kinase A in the presence of [gamma-32P] ATP in a cell-free system, but MLSI-SA was not phosphorylated significantly. A potent and selective inhibitor of protein kinase A (N-[2(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89)) showed 50% inhibition of the Luk-I-induced cell lysis at 0.5 nM. Thus, it is concluded that the phosphorylation of the Ser138 residue in the 4-residue segment K135K1361137S138 of LukS-I is important for the leukocytolysis of HPMNLs.
DOI： https://doi.org/10.1271/bbb.66.328
Other Link： https://www.jstage.jst.go.jp/article/bbb/66/2/66_2_328/_pdf
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Tyrosine72 Residue at the Bottom of Rim Domain in LukF Crucial for the Sequential Binding of the Staphylococcal gamma-Hemolysin to Human Erythrocytes Reviewed
Kenji Yokota, Yoshiyuki Kamio
Bioscience, Biotechnology, and Biochemistry 64 ( 12 ) 2744 - 2747 2000.12
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Staphylococcal bi-component cytotoxins, leukocidin (Luk), Panton-Valentine leukocidin (PVL), and γ-hemolysin (Hlg) consist of LukF and LukS, LukF-PV and LukS-PV, and LukF and Hlg2, respectively, and Luk and Hlg share LukF. LukF-PV can not substitute for LukF for Hlg, despite 73% identity in amino acid sequence and close similarity in the 3-dimensional structure between them. Here, we demonstrated that the absence of hemolytic activity of LukF-PV in cooperation with Hlg2 is due to the failure of the binding of LukF-PV to human erythrocytes. We identified Y72 residue at the bottom of rim domain in LukF as the crucial residue for its binding, which is a prerequisite to the subsequent binding of Hlg2 to human erythrocytes. The data obtained showed that a mutant of LukF-PV in which T71 residue was replaced by the corresponding residue of LukF, Y72, endowed LukF-PV with the binding capability to human erythrocytes which was accompanied by its hemolytic activity in the presence of Hlg2.
DOI： https://doi.org/10.1271/bbb.64.2744
Other Link： https://www.jstage.jst.go.jp/article/bbb/64/12/64_12_2744/_pdf
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Crystal Structure of Staphylococcal LukF Delineates Conformational Changes Accompanying Formation of a Transmembrane Channel Reviewed International coauthorship
Rich Olson, Hirofumi Nariya, Kenji Yokota, Yoshiyuki Kamio, Eric Gouaux
Nature Structural Biology IF:13.563 6 ( 2 ) 134 - 140 1999.02
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Staphylococcal LukF, LukS, HgammaII, and alpha-hemolysin are self-assembling, channel-forming proteins related in sequence and function. In the alpha-hemolysin heptamer, the channel-forming beta-strands and the amino latch make long excursions from the protomer core. Here we report the crystal structure of the water soluble form of LukF. In the LukF structure the channel-forming region folds into an amphipathic, three-strand beta-sheet and the amino latch forms a beta-strand extending a central beta-sheet. The LukF structure illustrates how a channel-forming toxin masks protein-protein and protein-membrane interfaces prior to cell binding and assembly, and together with the alpha-hemolysin heptamer structure, they define the end points on the pathway of toxin assembly.
DOI： https://doi.org/10.1038/5821
Other Link： http://www.nature.com/nsmb/journal/v6/n2/full/nsb0299_134.html
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Further Study on the Two Pivotal Parts of Hlg2 for the Full Hemolytic Activity of Staphylococcal gamma-Hemolysin Reviewed
Kenji Yokota, Noriko Sugawara, Hirofumi Nariya, Jun Kaneko, Toshio Tomita, Yoshiyuki Kamio
Bioscience, Biotechnology, and Biochemistry 62 ( 9 ) 1745 - 1750 1998.09
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Staphylococcal gamma-hemolysin consists of LukF of 34 kDa and Hlg2 (or H gamma II) of 32 kDa, which cooperatively lyse human and rabbit erythrocytes. Our previous data showed that the 5-residue segment K23R24L25A26I27 of Hlg2 is pivotal for the hemolytic activity [Nariya, H. and Kamio, Y., Biosci. Biotechnol. Biochem., 59, 1603-1604 (1997)]. Here, we identify an additional amino acid residue in Hlg2 necessary for the full gamma-hemolysin activity by measuring the toxin activity of Hlg2 mutants in the presence of LukF. The data obtained showed that Arg217 of Hlg2 is an additional pivotal amino acid residue besides the KRLAI segment for the full Hlg2-specific function in gamma-hemolysin. We also report evidence that the Hlg2 mutants showing a low or null hemolytic activity in the presence of LukF towards human erythrocytes had low or no binding activity to the cells, resulting in failure of formation of the ring-shaped pore-forming complex on the erythrocytes.
DOI： https://doi.org/10.1271/bbb.62.1745
Other Link： https://www.jstage.jst.go.jp/article/bbb/62/9/62_9_1745/_pdf