Evidence for a beta 1 integrin fibronectin receptor in Candida tropicalis

The binding of Candida tropicalis to fibronectin (FN) was studied in order to characterize the FN receptor in this species. FN binding was saturable at a concentration of 1.8 x 10(-9) M and exhibited a Kd of 2.3 x 10(-9) M and a receptor density of 854 receptors per cell. Extracts of C. tropicalis cell membrane at dilutions of 1:100-1:1000 significantly inhibited the binding of 3H-labeled FN to C. tropicalis cells (P < .03). Purified FN, antibodies to the integrin alpha 5 beta 1 (FN receptor on human placenta), and antibodies specific for the integrin beta 1 subunit recognized a C. tropicalis membrane protein of 125 +/- 25 kDa on immunoblots. Immunoprecipitation of radiolabeled proteins from C. tropicalis with purified human FN yielded a protein of 105 +/- 15 kDa. Thus, C. tropicalis expresses a protein with antigenic and functional similarity to the vertebrate beta 1 integrin FN receptor.