A collagen-binding protein produced by Aeromonas hydrophila

The gastrointestinal pathogen Aeromonas hydrophila strain A186 produces a collagen-binding protein (CNBP) which is found extracellularly and loosely associated with the cell surface. The cell-associated CNBP was purified by sequential ammonium sulphate precipitation, size-exclusion chromatography and ion-exchange chromatography, or by sequential ammonium sulphate precipitation and affinity chromatography with collagen-Sepharose. The purified CNBP was homogeneous in SDS-PAGE, and had a mol. wt of c. 98 kDa. Cyanogen bromide cleavage of the CNBP destroyed collagen-binding activity; however, enzymic digestion with Staphylococcus aureus V8 protease generated > 10 polypeptide fragments, from which a 30-kDa polypeptide contained the strongest collagen-binding activity. Binding of collagen by the CNBP was restricted to the alpha1 (I) chain of the collagen molecule and binding seemed to involve both the carbohydrate moieties and certain peptide sequences on the collagen. Collagen-saccharides generated by alkaline hydrolysis inhibited collagen binding by A. hydrophila. Also, glycosidase digestion and chemical alteration of the carbohydrate residues of collagen reduced its ability to be bound by the CNBP. Collagen-homologous synthetic peptides inhibited binding of 125I-collagen by the bacteria.