Artificial cell adhesive proteins engineered by grafting the Arg-Gly-Asp cell recognition signal: factors modulating the cell adhesive activity of the grafted signal.

An artificial cell adhesive protein could be engineered by grafting the RGDS tetrapeptide, the core sequence of the major cell adhesive site of fibronectin, to a truncated form of Staphylococcal protein A (tSPA) via cassette mutagenesis of the tSPA expression vector pRIT2T [T. Maeda et al. (1989) J. Biol. Chem. 264, 15165-15168]. We synthesized a panel of tSPA derivatives grafted with various RGDS-containing oligopeptides to address the problem of how the cell adhesive activity of the resulting tSPA derivatives was affected by the length and amino acid sequence of the grafted oligopeptides and by the sites on tSPA where the extra oligopeptides were inserted. The results showed that (i) the amino acid residues flanking the RGDS core sequence played a key role in modulating the cell adhesive activity of the grafted RGDS signal; (ii) at least two sites on tSPA, each corresponding to on e of the two HindIII sites of pRIT2T, were competent in sustaining the cell adhesive activity of the grafted signal; and (iii) the divalent tSPA containing the RGDS signal at both sites was more active than monovalent derivatives containing only one signal at either site. These results provide a strategic basis for engineering of artificial cell adhesive proteins by grafting the RGDS signal.