BINDING OF PLASMA FIBRONECTIN TO CANDIDA-ALBICANS OCCURS THROUGH THE CELL-BINDING DOMAIN

Candida albicans yeast cells bind soluble human plasma fibronectin (Fn ) through a glycoprotein receptor (adhesin) located on the cell surfac e. This work demonstrates that a 120 kDa proteolytic fragment of Fn en compassing the cell binding domain binds more avidly to the yeast cell adhesin than does the parent Fn molecule. The presence of binding of Fn fragments containing heparin- and gelatin-binding domains of Fn cou ld not be detected. The binding of the 120 kDa fragment is inhibited b y a monoclonal antibody to the cell binding domain containing the amin o acid sequence, Arginine-Glycine-Aspartic acid (RGD) as well as by an RGD-containing similar to 23-mer Fn peptide, but not with heparin or GRGDSPL. The fact that the cell binding domain of soluble Fn binds mor e avidly than does the parent molecule may explain the difference in t he interaction of soluble Fn and immobilized Fn with Candida. It is po ssible that, upon immobilization, Fn may expose domains of the molecul e previously unexposed when the molecule is in the soluble state.