Conformational resemblance between the structures of integrin-activating pentapetides derived from βig-h3 and RGD peptide analogues in a membrane environment

The peptides NKDIL and EPDIM, respectively derived from the 2nd and 4th domains of βig-h3, were fully active in mediating cell adhesion through interactions with α₃β₁ integrin [Biochem. Biophys. Res. Commun. 294 (2002) 940; J. Biol. Chem. 275 (2000) 30907]. Here, the conformational differences between NKDIL and EPDIM in water and in membrane environments were studied using CD spectroscopy, and their structures in sodium dodecylsulfate micelles were determined by NMR. The two peptides adopt β-turn structures like RGD peptides, and have more regular structures in micelles than in aqueous buffers. EPDIM shows a distorted type I β-turn for the PDIM segment in a membrane environment. The structure of NKDIL is similar with the standard type I′ β-turn, but shows large backbone flexibility even in a membrane environment. The conformational change of the 4th repeated domain of βig-h3 in micelle solutions suggests that the Asp-Ile motif of the 4th fas-1 domain (EPDIM) would be solvent-exposed and could interact with integrin α₃β₁ in a membrane environment. The present study provides a structural basis of βig-h3 function and information for the development of integrin-regulating drugs involving the wound healing protein.