Exosites, Allostery, & Active Site in MMP Engagement of Elastin, Collagen, and Heparin from the Matrix

Abstract

MMP‐12 and MT1‐MMP digest protease‐resistant elastin and collagen in inflammatory diseases. ProMMP‐7 is activated by glycosaminoglycans (GAGs). How do these matrix components interact with these MMPs? We sought to locate using NMR the binding sites of elastin and collagen triple‐helical peptides upon MMP‐12, collagen upon MT1‐MMP, and heparin fragments upon proMMP‐7. Two remote loops enhance its degradation of elastin substrates. Mutations at both remote loops plus the active site knock down specifically the elastase activity to that of the negative control. A collagen triple‐helical peptide crosses the active site of MMP‐12 at an angle and may separate the peptide chains in the primed positions for one chain to fit into the narrow slot formed by the primed subsites. Solubilized collagen binds a patch across blades III and IV of the β‐propeller of the hemopexin domain of MT1‐MMP. Binding of 6 to 12‐mer pieces of heparin to proMMP‐7 achieves part of the GAG‐dependent activation. The binding site is on the back of the catalytic domain. Adjustments in the interface between catalytic and pro‐domains and activation can then follow, suggesting allosteric communication at long range. Overall, pericellular proteolysis can engage remote surfaces of MMPs. Supported by NIH grants GM57289 and CA98799 and AHA grant 0855714G.