Structure and Function of Procollagen C-Proteinase (mTolloid) Domains Determined by Protease Digestion, Circular Dichroism, Binding to Procollagen Type I, and Computer Modeling

作者：Aleksander L. Sieroń, Anna Tretiakova, Bradford A. Jameson, Mark L. Segall, Sissel Lund‐Katz, Muhammad Tariq Masood Khan, Shiwu Li, Walter Stöcker · 发表于：Biochemistry · 年份：2000 · DOI：10.1021/bi992312o · 被引用次数：58 · 研究领域：Protease and Inhibitor Mechanisms、Connective tissue disorders research、Peptidase Inhibition and Analysis

Procollagen C-proteinase-2 (pCP-2, mTld) is derived from the longest splicing variant of the gene encoding bone morphogenetic protein 1 (BMP-1). The variants have identical amino terminal signal peptides, prodomains and astacin-like protease domains. However, they differ in the length of their carboxy terminal part, which in pCP-2 has the composition CUB1, CUB2, EGF-like1, CUB3, EGF-like2, CUB4, CUB5, and C-tail. In the shorter form, pCP-1 (i.e., BMP-1), the sequence ends after the CUB3-domain. Using a combination of mutagenesis and structural approaches, we have investigated the structure and function of subfragments of pCP-2. The full-length latent recombinant enzyme and its N-terminally truncated form lacking the prodomain were tested for their enzymic activity. The intact protein showed only partial processing of procollagen type I, whereas the truncated form expressed enzymic activity indistinguishable from its native counterpart purified from chick embryo tendons. These results clearly demonstrated that the prodomain is required for the latency of the enzyme but not for its correct folding. Limited proteolysis of the recombinant protein with alpha-chymotrypsin produced four discrete fragments revealing the location of cleavage sites between the repetitive CUB/EGF domains. The results provide evidence that the CUB sequences form independently folded modules that are stabilized by two pairs of internal disulfide bridges. The modules are linked to each other by more flexib...