Structural basis of collagen recognition by integrin alpha 2 beta 1

We have determined the crystal structure of a complex between the I domain of integrin alpha 2 beta 1 and a triple helical collagen peptide containing a critical GFOGER motif. Three loops on the upper surface of the I domain that coordinate a metal ion also engage the collagen, with a collagen gluta mate completing the coordination sphere of the metal. Comparison with the u nliganded I domain reveals a change in metal coordination linked to a reorg anization of the upper surface that together create a complementary surface for binding collagen. Conformational changes propagate from the upper surf ace to the opposite pole of the domain, suggesting both a basis for affinit y regulation and a pathway for signal transduction. The structural features observed here may represent a general mechanism for integrin-ligand recogn ition.