SUSCEPTIBILITY OF TYPE-I COLLAGEN CONTAINING MUTATED ALPHA-1(1) CHAINS TO CLEAVAGE BY HUMAN NEUTROPHIL COLLAGENASE

Two members of the matrix metalloproteinase family which can cleave na tive types I, II and III triple helical collagens are collagenases fro m fibroblasts and neutrophils. These enzymes are the products of diffe rent genes which share structural motifs but are only 57% identical. I n this study, we determined the site of cleavage in the alpha1 (I) cha ins and showed that the neutrophil collagenase acted at the same site as the fibroblast collagenase. We also used collagens as substrates wh ich were generated by site-directed mutagenesis of the murine Colla 1 gene and found that the pattern of susceptibility to cleavage by purif ied neutrophil collagenase was indistinguishable from that previously described for the fibroblast collagenase. Collagens containing substit utions of Pro for Ile-776 (P1) were not cleaved; whereas those contain ing substitutions of Met for Ile-776 were cleaved. Type I collagen whi ch contained alpha1(I) chains in which there were double substitutions of Pro for Gln-774 (P2) and Ala-777 (P2') were also not cleaved. Thes e type I collagens contained wild type alpha2(I) chains as well as mut ant alpha1(I) chains in the mixed helical trimers; the alpha2(I) chain in the trimers containing the resistant alpha1(I) chains were also no t cleaved by the neutrophil collagenase.