1999 Fiscal Year Final Research Report Summary
Molecular Analysis of Multiple Forms of the Streptococcus mutans Dextranase
| Project/Area Number |
09671867
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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 |
Morphological basic dentistry
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| Research Institution | Showa University |
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Principal Investigator |
GOTO Nobuichi Showa University, School of Dentistry, Professor, 歯学部, 教授 (10077175)
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| Co-Investigator(Kenkyū-buntansha) |
IGARASHI Takeshi Showa University, School of Dentistry, Associate Professor, 歯学部, 助教授 (10159585)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Dextranase / Multiple form / Streptococcus mutans / Cariogenic bacteria / Mutans streptococci |
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| Research Abstract |
Molecular analysis of multiple forms of the Streptococcus mutans dextranase was studied by the approach of molecular genetics. In order to find out common characteristics of dextrnase (Dex) of cariogenic bacteria, complete nucleotide sequence of the S. downei dextranase gene was determined and compared with those of S. mutans and S. sobrinus. Homology analysis showed that the Dex was constituted by a conserved region and two variable regions. In addition, Dex of three species was detected as active multiple forms in Dex active staining. We, therefore, speculated that the conserved region was essential for Dex activity and the variable regions of N- and C-terminals were responsible for the multiple forms of the Dex.. On the basis of this speculation, we constructed mutants at two variable regions on the S. mutans Dex by genetic manipulation and examined influence to the multiple forms and activity of the Dex. Mutants within a C-terminal variable region showed the multiple forms with the Dex activity. Mutants defective both the C-terminal variable region and a part of the conserved regions disappeared not only the multiple forms but also the activity. On the other hand, mutants within a N-terminal variable region of the C-terminal mutant with Dex activity did not show both the multiple forms and the activity. These results indicated that the multiple forms of the Dex was responsible for degradation of the variable region of C-terminus and suggested that the conserved region would contain the catalytic sites such as active and substrate binding sites.
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