Molecular interactions of alanine-rich and proline-rich regions of cell surface protein antigen c in Streptococcus mutans.
BACKGROUND
Streptococcus mutans has been implicated as a primary causative agent of dental caries in humans, and its cell surface protein antigen c (PAc) is known to be associated with sucrose-independent adhesion to tooth surfaces. PAc is composed of several domains, including an N-terminal signal sequence, an alanine-rich repeat region (A-region), a proline-rich repeat region (P-region), and an anchor region.


METHODS
To investigate the functions of each domain, an A-region-deficient mutant strain of S. mutans was constructed, and recombinant PAc and A- and P-region proteins were also constructed. The interactions of each domain with the recombinant proteins were analyzed using surface plasmon resonance spectroscopy with a biomolecular interaction analyzing system.


RESULTS
The A-region-deficient mutant strain showed the lowest levels of adherence to saliva-coated hydroxyapatite. Furthermore, findings in an immunoblot assay indicated that the A-region protein reacted strongly with proline-rich proteins in saliva, while the recombinant P-region protein interacted more quickly with PAc than the recombinant A-region protein.


CONCLUSIONS
These results suggest that the A-region has a strong relationship with adhesion to tooth surfaces, while the P-region has a high affinity for PAc.
Matsumoto-Nakano
M
M
Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan.
Tsuji
M
M
Amano
A
A
Ooshima
T
T
D000409:Alanine / Q000276:immunology*; D000915:Antibody Affinity / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D001422:Bacterial Adhesion / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology*; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes; D006801:Humans; D009154:Mutation / Q000235:genetics; D010455:Peptides / Q000276:immunology; D011392:Proline / Q000276:immunology*; D055232:Proline-Rich Protein Domains; D011994:Recombinant Proteins; D012471:Salivary Proteins and Peptides / Q000276:immunology; D013295:Streptococcus mutans / Q000235:genetics / Q000276:immunology*
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; D020099:Coated Materials, Biocompatible; D000939:Epitopes; D010455:Peptides; D011994:Recombinant Proteins; D012471:Salivary Proteins and Peptides; D017886:Durapatite; D011392:Proline; D000409:Alanine