PB0408 - Regulation of collagen binding integrins by alpha 7 and C helix

Background: In collagen binding integrin, the c-terminal helix, α7 (from Glu318 to Phe333) is the longest helix in α2 I domain where half of its 16 amino acids are of hydrophobic nature. Crystal structure data of α2 I domain bound to the collagen peptide GFOGER showed a large (10Å) shift of α7 (open conformation). Subtle changes in metal coordination are linked to extensive secondary and tertiary changes that create a complementary surface for binding collagen. The principal conformational changes occur in three regions. These are a movement of the MIDAS loops and helix α1 as a direct consequence of a change in metal coordination; a “slinking” motion between the C helix and helix α6, which opens up the collagen binding site; and the large shift of α7, which propagates structural changes to the opposite pole of the domain. To understand the role of α7 and c-helix in regulation of integrin activity, we expressed different mutants of α2 I domain and also α1 I domain.

Aims: Understanding the role of α7 and c-helix in regulation of integrin activity

Methods: Site-directed mutagenesis and Phage display

Results: Substitution of the hydrophobic amino acids in α7 or deletion of c-helix activate integrin I domain.

Conclusion(s): Hydrophobic amino acids in α7 together with the c-helix playing a regulatory role in collagen binding.