MMP-PAR1 interactions. (A) Structure of the proMMP1 zymogen. The catalytic zinc is indicated as a red ball within the catalytic domain. (B) Cleavage sites for MMP-1, MMP-13, and thrombin in PAR1 and resulting tethered ligands. (C) Top: N-terminal region encompassing the PAR1-tethered ligand showing the cleavage sites for MMP-1 and thrombin. Bottom: Structural model of the catalytic groove of MMP-1 bound to the N-terminal domain of PAR1, illustrating the catalytic zinc coordinated to the PAR1 scissile D-P bond. The model was created using the x-ray structures of MMP-1 and MMP-8 bound to peptide inhibitors as templates.^49,50