| Project/Area Number |
16590376
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Bacteriology (including Mycology)
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| Research Institution | Tokushima Bunri University |
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Principal Investigator |
SAKURAI J. Tokushima Bunri Univ., Fac. Pharm. Sci., Full Professor, 薬学部, 教授 (80029800)
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| Co-Investigator(Kenkyū-buntansha) |
NAGAHAMA M. Tokushima Bunri Univ., Fac. Pharm. Sci., Assis. Professor, 薬学部, 助教授 (40164462)
KOBAYASHI K. Tokushima Bunri Univ., Fac. Pharm. Sci., Res. associate, 薬学部, 助手 (90170315)
TSUGE H. Tokushima Bunri Univ., Full Professor, 健康科学研究所, 教授 (40299342)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2005: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2004: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Clostridium perfrngens / alpha-toxin / Bacillus cereus / sphinogmyelinase / crystal analysis / hemolysis / divalent metal cation / phospholipid / スフィンゴミエリン / スフィンゴシン1-リン酸 |
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| Research Abstract |
Sphingomyelinase (SMase) from Bacillus cereus (Bc-SMase) hydrolyzes sphingomyeiin to phosphocoline and ceramide with the essential divalent metal ion. Bc-SMase is a homologous enzyme of mammalian neutral SMase (nSMase), and mimics the action of the endogenous mammalian nSMase in causing differentiation, development, aging and apoptosis, thus Bc-SMase would be a model for the poorly characterized mammalian nSMase. The metal ion activation of sphingomyelinase activity of Bc-SMase was in the order of Co^<2+>>=Mn^<2+>>=Mg^<2+>>>Ca^<2+>>=Sr^<2+>. The first crystal structures of Bc-SMase with these metal ions were determined. The water bridged double divalent metal ions at the center of cleft in both of Co^<2+> and Mg^<2+> were concluded to be the catalytic architecture to exert the sphingomyelinase activities. On the other hands, the architecture of Ca^<2+> binding at the site was different from that of Ca^<2+> and Mg^<2+>. There is the other binding site of these metal ions at one side edge of the cleft. The crystal structure of the enzyme with Mg^<2+> or Co^<2+> would provide the common structure basis among phosphohydrolases belonging DNase I like folding superfamily, due to their common architecture of the catalytic amino acid residues. In addition, the structural features and site directed mutagenesis suggest that the specific β-hairpin with the aromatic amino acid residues participates in binding to membrane SM and the substrate SM. Therefore, It is apparent that the 3D structure of alpha-toxin is different from that of Bc-SMase, although the toxin hemolyzes the same sheep erythrocytes as Bc-SMase. From the results, the mechanism of hemolysis induced by the toxin seems to be is different from that of Bc-SMase.
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