Expression of the cell‐binding domain of human fibronectin in E. coli

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Abstract
Two cDNA subfragments containing the cell‐attachment site of human fibronectin (FN) were expressed as β‐galactosidase fusion proteins in E. coli. The products were purified to homogeneity by monoclonal antibody affinity chromatography and assayed for activity in a standard cell‐adhesion assay. A fusion protein containing an 80 kDa fragment of human FN appeared functionally equivalent to intact FN purified from human plasma, whereas a truncated fusion protein of 33 kDa still containing a previously postulated cell‐attachment site was approx. 50‐fold less active. Our study establishes a system for analyzing adhesive protein function by DNA manipulation, rules out any major role for eukaryotic post‐translational modifications in FN adhesive function, and localizes additional functional activity to a 1.3 kb region.