LOCAL CONFORMATIONAL-CHANGES OF VITRONECTIN UPON ADSORPTION ON GLASS AND SILANE SURFACES

The conformation of vitronectin (Vn) in solution and adsorbed to hydro philic and hydrophobic glass was studied using the polarity-sensitive fluor acrylodan. Free sulfhydryl groups of vitronectin were labeled wi th acrylodan under nondenaturing conditions. The number and location o f the free sulfhydryl groups were determined by cleavage with either f ormic acid or cyanogen bromide followed by polyacrylamide gel electrop horesis. Based upon published amino acid sequences of Vn, the fluoresc ence of acrylodan-labeled Vn (Ac-Vn) fragments is consistent with free sulfhydryls being located at cysteine residues 196 and 274. Conformat ional changes upon adsorption on glass and silanized glass surfaces pl aced the free sulfhydryl residues in a more hydrophobic environment th an was observed when Vn was in PBS solution. Small but statistically s ignificant quenching of Ac-Vn fluorescence with iodide could be explai ned in terms of a two-site model. Results of this study suggest that t he domains surrounding the free sulfhydryl groups of vitronectin exper ience different environments in solution and adsorbed to surfaces. (C) 1994 Academic Press, Inc.