Crystal structure of a Trimeresurus mucrosquamatus venom metalloproteinase providing new insights into the inhibition by endogenous tripeptide inhibitors

The crystal structure of TM-1, a P-I class snake-venom metalloproteinase (SVMP) from the Trimeresurus mucrosquamatus venom, was determined at 1.8-Å resolution. The structure exhibits the typical feature of SVMPs and is stabilized by three disulfide linkages. The active site shows a deep S1' substrate-binding pocket limited by the non-conserved Pro174 at the bottom. Further comparisons with other SVMPs suggest that the deep S1' site of TM-1 correlates with its high inhibition sensitivity to the endogenous tripeptide inhibitors. Proteolytic specificity analysis revealed that TM-1 prefers substrates having a moderate-size and hydrophobic residue at the P1' position, consistent with our structural observation.