Purification and Characterization of Galactosephilic Component Present on the Cell Surfaces ofStreptococcus sanguisATCC 10557

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Abstract
Previous studies have indicated that a galactosephilic component present on the bacterial cell surfaces of Streptococcus sanguis ATCC 10557 may be responsible for the salivary glycoprotein‐medtated binding of the cells. The purpose of this study was to investigate the purification and characterization of galactosephilic cell surface component from S. sanguis ATCC 10557. A galactosephilic component involving fibrils on the cell surfaces was isolated by the techniques of freezing and thawing, and purified by an affinity chromatography on β‐d‐galactose binding‐Bio‐Gel P‐2 followed by gel filtrations on Bio‐Gel P‐150 and on Bio‐Gel P‐30. Both disk gel electrophoresis and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis showed that the purified product was homogeneous. The isoelectric point of the purified sample was 8.5 to 9.0. Treatment of the purified sample with pronase E reduced remarkably either the hemagglutinating activity or the precipitation reaction with proline‐rich glycoprotein in human parotid saliva, suggesting that the active site may be present on the peptide moieties. When sugar specificity was examined by hemagglutination‐inhibition test, d‐galactose was the strongest inhibitor. The results of this study suggest that the galactosephilic component may be a bacterial lectin.