The latent precursors of the matrix metalloproteinases (MMPs) are converted by (4-aminophenylmercuric)acetate to active forms that lose their propeptide as a result of autolysis. C.D. and an active site mutant of progelatinase A (MMP2) were used to demonstrate that, although propeptide removal is accompanied by a decrease in the enzyme's beta;-sheet content, the initial activation is achieved with only minor modifications to the conformation. Mixing activated gelatinase A with the natural inhibitor, TIMP-1, resulted in conformational changes that were absent when a synthetic inhibitor was used. The relevance of these results to MMP activation and inhibition is discussed.
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