IDENTIFICATION OF SALIVARY BASIC PROLINE-RICH PROTEINS AS RECEPTORS FOR CANDIDA-ALBICANS ADHESION

The adherence of Candida albicans cells to oral surfaces is believed t o be an important step in the development of oral candidosis. Electrop horetically separated parotid salivary proteins were transferred to ni trocellulose membranes and incubated with [S-35]methionine-radiolabell ed C. albicans cells in a cell overlay adherence assay. A subset of fo ur proteins with apparent molecular masses of 17, 20, 24 and 27 kDa (d esignated bands A-D) acted as receptors for cells of C. albicans ATCC 10261 and four clinical C. albicans isolates, in overlay assays. The N -terminal amino acid sequence of bands A-D indicated that these protei ns were members of the basic proline-rich protein (hPRP) family. Diges tion of protein A with endoproteinase Glu-C resulted in a single band (designated Ap) detected by Coomassie blue staining after SDSPAGE. Thi s band was not bound by C. albicans cells in overlay assays and compri sed two fragments, designated ApN and ApC. These fragments had N-termi nal sequences corresponding to the N-terminal and post endoproteinase Glu-C cleavage site sequences of bPRP IB-6 and had molecular masses of 6189 and 4261 Da as determined by mass spectrometry. Thus intact bPRP IB-6, and other bPRPs, may act as receptors for C. albicans adhesion.