Identification of amino acid sequences in fibrinogen γ-chain and tenascin C C-terminal domains critical for binding to integrin α(v)β₃

Integrin α(v)β₃ recognizes fibrinogen γ and α(E) chain C-terminal domains (γC and α(E)C) but does not require the γC dodecapeptide sequence HHLGGAKQAGDV^400-411 for binding to γC. We have localized the α(v)β₃ binding sites in γC using γC-derived synthetic peptides. We found that two peptides GWTVFQKRLDGSV^190-202 and GVYYQGGTYSKAS^346-358 block the α(v)β₃ binding to γC or α(E)C, block the a{v)β₃-mediated clot retraction, and induce the ligand-induced binding site 2 (LIBS2) epitope in a{v)β₃. Neither peptide affects fibrinogen binding to α(IIb)β₃. Scrambled or inverted peptides were not effective. These results suggest that the two γC-derived peptides directly interact with α(v)β₃ and specifically block a{v)β₃-γC or α(E)C interaction. The two sequences are located next to each other in the γC crystal structure, although they are separate in the primary structure. Asp-199, Ser-201, Gln-350, Thr-353, Lys- 356, Ala-357, and Ser-358 residues are exposed to the surface. This suggests that the two sequences are part of α(v)β₃ binding sites in fibrinogen γC domain. We also found that tenascin C C-terminal fibrinogen-like domain specifically binds to α(v)β₃. Notably, a peptide WYRNCHRVNLMGRYGDNHSQGVNWFHWKG from this domain that includes the sequence corresponding to γC GVYYQGGTYSKAS^346-358 specifically binds to α(v)β₃, suggesting that fibrinogen and tenascin C C-terminal domains interact with α(v)β₃ in a similar manner.