The latency of the human fibroblast collagenase precursor depends on an internal cysteine residue.

The proenzyme form of human fibroblast collagenase has been expressed in E. coli from its cDNA clone and has been shown to be functionally identical to the human enzyme. Mutants at one of three cysteine residues were constructed by site-directed mutagenesis of the cDNA and their relative activities compared to the wild type enzyme. A cysteine contained in the propeptide domain of procollagenase and other matrix metalloproteinases was shown to be essential for maintaining the proenzyme in an inactive state. A model to explain the importance of this highly conserved cysteine to the maintenance of latency is discussed.