Characterization of a cell-surface protein antigen of hydrophilic Streptococcus mutans strain GS-5

Ohta, H.; Kato, H.; Okahashi, N.; Takahashi, I.; Hamada, S.; Koga, T.

Journal of General Microbiology 135(4): 981-988


ISSN/ISBN: 0022-1287
PMID: 2600589
Accession: 039519335

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Fourteen strains of Streptococcus mutans serotype c were examined for their cell-surface protein antigens in terms of hydrophobicity, Mr and immunochemical specificities. Thirteen strains were hydrophobic, while strain GS-5 was markedly hydrophilic as compared to the other strains tested. Cell-surface protein antigens were then analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western immunoblotting. A protein antigen of Mr 190,000 (PAc) was found in cell extracts and culture supernatants of all the hydrophobic strains. Neither culture supernatant nor cell extract of strain GS-5 contained PAc. Strain GS-5, however, produced extracellularly a large amount of a protein of Mr 155,000 (PAGS-5) which reacted with rabbit anti-PAc serum. Immunodiffusion analysis showed that PAGS-5 lacked a part of the antigenic moieties in the PAc molecule. SDS-PAGE and radioimmunoassay showed a small amount of PAGS-5 on the cell surface of strain GS-5. These findings suggest that PAGS-5 may correspond to PAc which lacks a region participating in binding of PAc to the streptococcal cell.