Step 1 is the binding of the triple-helix to the MMP. Step 2 is the unwinding of the triple-helix, allowing access to individual strands. Step 3 is the binding of a single strand to the MMP active site. Step 4 is the hydrolysis of a single strand and release of product. For step 5, in rapid succession, the other two strands are bound and cleaved and the products are released. COL = collagen, C = catalytic domain, and H = hemopexin-like domain.