Properties of a protein from Staphylococcus capitis that binds human serum high density lipoprotein

A high density lipoprotein (HDL) binding component from the cell wall of Staphylococcus capitis, possessing both HDL binding and HDL precipitating activity, has been partially characterised. Growth of the bacteria on medium containing cysteine or in presence of CO2, was found to induce the synthesis of this factor. Analysis show an incorporation of radioactive amino acids into the factor, and also its sensitivity to trypsin, indicating strongly that the HDL binding factor is of protein nature. Gel-filtration experiments showed that the HDL binding protein had an elution volume corresponding to a molecular weight of about 150K. However, SDS-PAGE analysis of HDL binding protein, purified by affinity chromatography, showed that the 150K component was composed of subunits of a low molecular weight protein (7K). As judged by the incorporation of radiolabelled amino acids, the HDL binding protein may, under certain growth conditions, constitute as much as 15% of the total protein in the autolytic extract from the bacteria.