colH
Domain
The mature protein has 4 domains; a metalloprotease domain (S1, approximately residues 41-717), S2a (718-810, equivalent to PKD 1), S2b (811-904, equivalent to PKD 2) and a collagen-binding domain (S3, 905-1021) (PubMed:9452493, PubMed:9922257). The protein has an elongated shape, which lengthens further in calcium-chelated conditions; calcium-chelation also increases its susceptibility to exogenous proteases (PubMed:23561530). The S1 domain has the collagen hydrolytic activity (PubMed:18937627, PubMed:9452493). The metalloprotease S1 domain is composed of 3 subdomains which together resemble a saddle; an activator domain (residues 41-320), the catalytic peptidase subdomain (330-601) and a helper subdomain (609-721) (PubMed:23703618). Unlike the S2 domain in ColG, upon binding to Ca(2+) the midsections of S2a and S2b remain rigid; Ca(2+) binding confers thermostability (PubMed:25760606). Ca(2+)-binding also alters the orientation of the N-terminal linker of S2b so it lies along the long axis of the domain (PubMed:25760606). S3 has collagen-binding activity (PubMed:9452493). The structure of S3 becomes more thermostable when it is bound to Ca(2+) (PubMed:23144249). Isolated CBD S3 binds unidirectionally to the C-terminus of the collagen triple helix via a surface cleft (PubMed:23144249).
Function
Clostridial collagenases are among the most efficient degraders of eukaryotic collagen known; saprophytes use collagen as a carbon source while pathogens additionally digest collagen to aid in host colonization. Has both tripeptidylcarboxypeptidase on Gly-X-Y and endopeptidase activities; the endopeptidase cuts within the triple helix region of collagen while tripeptidylcarboxypeptidase successively digests the exposed ends, thus clostridial collagenases can digest large sections of collagen (PubMed:3002446). The full-length protein has collagenase activity, while both the 116 kDa and 98 kDa forms act on gelatin (PubMed:7961400). In vitro digestion of soluble calf skin collagen fibrils requires both ColG and ColH; ColG forms missing the second collagen-binding domain is also synergistic with ColH, although their overall efficiency is decreased (PubMed:18374061, PubMed:22099748). Digestion of collagen requires Ca(2+) and is inhibited by EDTA (PubMed:9452493). The activator domain (residues 119-388) and catalytic subdomain (330-601) open and close around substrate allowing digestion when the protein is closed (PubMed:23703618).
Post-translational modifications
Upon purification gives rise to 98 kDa, 105 kDa and 116 kDa (full-length) proteins, all of which have the same N-terminus (PubMed:7961400, PubMed:9922257).
Sequence Similarities
Belongs to the peptidase M9B family. Collagenase subfamily.
Cellular localization
- Secreted
Alternative names
Collagenase ColH, Class II collagenase, Gelatinase ColH, Microbial collagenase, colH