Partial characterization of a Candida albicans fimbrial adhesin

Abstract

Candida albicans is the primary etiologic agent of candidiasis, a disease that can vary from superficial mucosal lesions to life-threatening systemic or disseminated diseases. Strains of C. albicans have been reported to possess long, thin filamentous protein cell surface appendages termed fimbriae (R. B. Gardiner, M. Canton, and A. W. Day, Bot. Gaz. 143:534-541, 1982). These fimbriae were isolated, purified, and partially characterized. The major structural subunit of the fimbriae is a glycoprotein which consists of 80 to 85% carbohydrate (consisting primarily of D-mannose) and 10 to 15% protein. The molecular weight of the glycosylated fimbrial subunit is approximately 66,000, while unglycosylated protein has an approximate molecular weight of 8,644. The fimbriae function as adhesins mediating C. albicans binding to human buccal epithelial cells. Amino acid analysis of the purified fimbrial subunit indicates that the fimbrial subunit is composed of 50% hydrophobic amino acid residues. The N terminus of the fimbrial subunit is blocked to N-terminal sequencing.

Use of synthetic peptides to confirm that the Pseudomonas aeruginosa PAK pilus adhesin and the Candida albicans fimbrial adhesin possess a homologous receptor‐binding domain

“…Opportunistic pathogens such as P. aeruginosa, a Gram-negative bacterium, and C. albicans, a dimorphic yeast, employ several distinct adhesins to mediate attachment to host epithelial cells (Prince, 1992;Irvin, 1993;Cutler, 1991;Hostetter, 1994). P. aeruginosa and C. albicans can utilize long flexible filaments termed a pilus and a fimbria, respectively, to mediate their adherence to epithelial cell surfaces (Paranchych and Frost, 1979;Yu et al, 1994a). Pili and fimbriae mediating the attachment of pathogens to the surfaces of the host have been described previously (Irvin, 1990).…”

“…Although the adhesin is located on the structural subunit of the PAK pilus, it has been shown that the carboxy-terminal region of the PAK pilin is only exposed at the tip of the pilus where receptor binding occurs (Irvin, 1993;Lee et al, 1994). The C. albicans fimbrial adhesin was first described by Irvin and co-workers (Yu et al, 1994a). The major fimbrial subunit of the C. albicans fimbria is a 66 kDa protein that is highly glycosylated (85% of the molecular mass consists of carbohydrate, primarily D-mannose residues).…”

“…The culture conditions of P. aeruginosa and the preparation of PAK pili have been described previously (Paranchych et al, 1979). The protocol used to obtain fimbrial adhesins from C. albicans strain 40, a clinical isolate from an intensive-care-unit patient in Toronto General Hospital (Toronto, Ontario, Canada), has been described previously (Yu et al, 1994a).…”

“…The biotinylated adhesins were aliquoted and stored at 7 208C. PAK pili and C. albicans fimbriae were previously demonstrated to bind to asialo-GM 1 (bGal1-4bGal NAcb1-4bGal1-4bGlcceramide) Yu et al, 1994a). Hence, biotinylated PAK pili (Bt-PAK pili) and biotinylated fimbriae (Btfimbriae) were assayed for their ability to bind to asialo-GM 1 (Sigma) immobilized onto microtitre wells (0.5 m g per well).…”

“…The pilus consists of a polymer of a single protein subunit termed pilin (Irvin, 1990). While the C. albicans fimbriae have not been completely characterized, the major subunit of the fimbria is a 66 000 Da glycoprotein (Yu et al, 1994a). The receptor-binding domain (termed 'adhesintope') of the P. aeruginosa PAK pilin adhesin has been shown to reside in the carboxyterminal disulphide-looped region (PAK128-144) of the PAK pilin (Irvin et al, 1989;Lee et al, 1994;.…”