STRUCTURE-FUNCTION-RELATIONSHIPS IN THE TISSUE INHIBITORS OF METALLOPROTEINASES

The tissue inhibitors of metalloproteinases (TIMPs) are proteins that specifically inhibit the matrix metalloproteinases. They consist of tw o distinct structural and functional domains. In order to elucidate th e role of these domains, we have prepared mutants of TIMP-1 and TlMP-2 that tack a C-terminal domain. The N-terminal domain alone is an effi cient inhibitor of all the matrix metalloproteinases through interacti on with the enzyme catalytic domain. The C-terminal domain has at leas t two separate enzyme binding sites, one for gelatinase A and the othe r for stromelysin-1. The rate of inhibition of either enzyme is increa sed by interaction with the TIMP C-terminal domain. As no conformation al change is observed, we propose that the rate enhancement is due to an anchoring effect in which binding of the TIMP C-terminal domain ali gns the TIMP N-terminal domain with the enzyme active site. Site-direc ted mutagenesis of TIMP-1 has demonstrated that the N-terminal amino a cids, His7 and Gln9, are important for inhibition.