Identification and enzymatic characterization of two diverging murine counterparts of human interstitial collagenase (MMP-1) expressed at sites of embryo implantation

Remodeling of fibrillar collagen in mouse tissues has been widely attribute d to the activity of collagenase-3 (matrix metalloproteinase-13 (MMP-13)), the main collagenase identified in this species. This proposal has been lar gely based on the repeatedly unproductive attempts to detect the presence i n murine tissues of interstitial collagenase (MMP-1), a major collagenase i n many species, including humans. In this work, we have performed an extens ive screening of murine genomic and cDNA libraries using as probe the full- length cDNA for human MMP-1, We report the identification of two novel memb ers of the MMP gene family which are contained within the cluster of MMP ge nes located at murine chromosome 9. The isolated cDNAs contain open reading frames of 464 and 463 amino acids and are 82% identical, displaying all st ructural features characteristic of archetypal MMPs, Comparison for sequenc e similarities revealed that the highest percentage of identities was found with human interstitial collagenase (MMP-1), The new proteins were tentati vely called Mcol-A and Mcol-B (Murine collagenase-like e and B), Analysis o f the enzymatic activity of the recombinant proteins revealed that both are catalytically autoactivable but only Mcol-A is able to degrade synthetic p eptides and type I and II fibrillar collagen. Both Mcol-A and Mcol-B genes are located in the A1-A2 region of mouse chromosome 9, Mcol-A occupying a p osition syntenic to the human MMP-1 locus at 11q22. Analysis of the express ion of these novel MMPs in murine tissues revealed their predominant presen ce during mouse embryogenesis, particularly in mouse trophoblast giant cell s. According to their structural and functional characteristics, we propose that at least one of these novel members of the MMP family, Mcol-A, may pl ay roles as interstitial collagenase in murine tissues and could represent a true orthologue of human MMP-1.