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Platelet-interactive products of Streptococcus sanguis protoplasts
M C Herzberg1, P R Erickson, P K Kane
1Department of Preventive Sciences, School of Dentistry, University of Minnesota, Minneapolis 55455.
Infection and Immunity
|December 1, 1990
Summary
Streptococcus sanguis protoplasts released a class II antigen that inhibits platelet aggregation. This antigen is functionally and immunologically identical to the previously identified 65-kDa protein involved in platelet aggregation.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Streptococcus sanguis interacts with human platelets, potentially contributing to infective endocarditis.
- A class II antigen on S. sanguis cells has been implicated in platelet aggregation.
Purpose of the Study:
- To isolate and characterize a more native, platelet-interactive macromolecule (class II antigen) from S. sanguis.
- To investigate the role of protoplast-derived antigens in platelet aggregation.
Main Methods:
- Protoplasts were prepared from S. sanguis and cultured.
- Soluble proteins from culture media were isolated and tested for inhibition of platelet aggregation.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoaffinity chromatography were used for protein analysis.
- Protein fractions were further purified using gel filtration and ion-exchange chromatography.
Main Results:
- Protoplast-released products reactive with anti-class II antigen antibodies inhibited S. sanguis-induced platelet aggregation.
- SDS-PAGE identified several protein bands, including a 115-kDa fraction isolated via chromatography.
- This 115-kDa fraction contained N-formylmethionine, rhamnose, and diester phosphorus.
- Trypsinization of protoplast products yielded a 65-kDa fragment identical to the previously identified S. sanguis cell-derived class II antigen.
Conclusions:
- Cultured S. sanguis protoplasts release a class II antigen that inhibits platelet aggregation.
- The 65-kDa class II antigen derived from protoplasts is functionally and immunologically identical to the cell-surface antigen involved in platelet aggregation.