F Willenbrock, G Murphy, IR Phillips, K Brocklehurst
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 truncated mutants of prostromelysin-1 and progelatinase A and report that 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 performed by the C-terminal domain in the full-length enzyme.