THE 2ND ZINC ATOM IN THE MATRIX METALLOPROTEINASE CATALYTIC DOMAIN ISABSENT IN THE FULL-LENGTH ENZYMES - A POSSIBLE ROLE FOR THE C-TERMINAL DOMAIN

Domain deletion mutants of the matrix metalloproteinases consisting of the catalytic domain only contain two zinc atoms per molecule. One is essential for catalysis, while the other may fulfil a structural role . We have analysed the zinc contents of both the full-length and the t runcated mutants of prostromelysin-1 and progelatinase A and report th at the second zinc atom is not present in the full-length form of the proenzymes. Thus it seems likely that the role proposed for this zinc atom in maintaining the structure of the enzyme catalytic domain is pe rformed by the C-terminal domain in the full-length enzyme.