Susceptibility of Type I Collagen Containing Mutated α1(1) Chains to Cleavage by Human Neutrophil Collagenase

Abstract

Two members of the matrix metalloproteinase family which can cleave native types I, II and III triple helical collagens are collagenases from fibroblasts and neutrophils. These enzymes are the products of different genes which share structural motifs but are only 57% identical. In this study, we determined the site of cleavage in the α1(I) chains and showed that the neutrophil collagenase acted at the same site as the fibroblast collagenase. We also used collagens as substrates which were generated by site-directed mutagenesis of the murine Col1a1 gene and found that the pattern of susceptibility to cleavage by purified neutrophil collagenase was indistinguishable from that previously described for the fibroblast collagenase. Collagens containing substitutions of Pro for Ile-776 (P₁) were not cleaved; whereas those containing substitutions of Met for Ile-776 were cleaved. Type I collagen which contained α1(I) chains in which there were double substitutions of Pro for Gln-774 (P₂) and Ala-777 (P₂′) were also not cleaved. These type I collagens contained wild type α2(I) chains as well as mutant α1(I) chains in the mixed helical trimers; the α2(I) chain in the trimers containing the resistant α1(I) chains were also not cleaved by the neutrophil collagenase.