Characterization of a Salivary Agglutinin Reacting with a Serotype c Strain of Streptococcus mutans

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Abstract
A protein, which can agglutinate a S. mutans serotype c strain, was isolated from human parotid saliva by affinity adsorption of the salivary agglutinin to the microorganism followed by a desorption with a 10 mM phosphate buffer. The agglutinin was subjected to preparative ultracentrifugation, gel filtration and ultrafiltration. The native purified agglutinin was active only in the presence of Ca. Polyacrylamide gel electrophoresis, analytical centrifugation, and analyses of amino acids and carbohydrates showed that the negative agglutinin was a fucose-rich glycoprotein with a carbohydrate content of 45% and a MW of at least 5 .times. 106. After sodium dodecyl sulfate treatment the MW was 4.4 .times. 105. There was a low content of proline and a high content of aspartic acid, serine and threonine. The concentration of agglutinin in parotid saliva is < 0.5 % of total protein. It has high biological activity; 0.1 .mu.g agglutinin causes a rapid aggregation of .apprx. 108 bacteria.