The following text describes a protein:
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. Active on soluble type I collagen, insoluble collagen, azocoll, soluble PZ-peptide (all collagenase substrates) and gelatin. The full-length protein has collagenase activity, while the in vivo derived C-terminally truncated shorter versions only act on gelatin. In vitro digestion of soluble calf skin collagen fibrils requires both ColG and ColH; ColG forms missing the second collagen-binding domain are also synergistic with ColH, although their overall efficiency is decreased. The activator domain (residues 119-388) and catalytic subdomain (389-670) open and close around substrate using a Gly-rich hinge (387-397), allowing digestion when the protein is closed. Binding of collagen requires Ca(2+) and is inhibited by EGTA; the collagen-binding domain (CBD, S3a plus S3b) specifically recognizes the triple-helical conformation made by 3 collagen protein chains in the triple-helical region. Isolated CBD (S3a plus S3b) binds collagen fibrils and sheets of many tissues.
Miscellaneous:
MISCELLANEOUS: Clostridial collagenases enable the bacteria to infiltrate and colonize host tissue, and contribute to gas gangrene (myonecrosis) pathogenesis.
Subcellular Localization:
Secreted.
Domain:
The mature protein has 4 domains; a metalloprotease domain (S1, approximately residues 111-786), S2 (877-882, equivalent to PKD), and 2 collagen-binding domains (CBD) S3a (997-1003) and S3b (1008-1118). The S1 domain has collagen hydrolytic activity. The metalloprotease S1 domain is composed of 3 subdomains which together resemble a saddle; an activator domain (residues 119-388), the catalytic peptidase subdomain (398-670) and a helper subdomain (679-790) joined by a Gly-rich hinge (387-397). The S2 domain (799-880, PKD) is flexible within a larger structure (S1 plus S2, residues 119-880). Binding to Ca(2+) renders the midsection of S2 more flexible; Ca(2+) binding confers thermostability. S3a and S3b each have collagen-binding activity; collagen is bound more efficiently when both S3a and S3b are present. CBD S3a plus S3b binds to many types of collagen in vitro and in vivo. The structure of CBD S3b becomes more compact and thermostable when it is bound to Ca(2+) and its N-terminal linker (approximately residues 1008-1020) changes from an extended alpha-helix to a beta-sheet anchored to the rest of the CBD. S3b may act as a Ca(2+)-activated molecular switch to trigger domain reorientation. Isolated CBD S3b binds unidirectionally to the C-terminus of the collagen triple helix via a surface cleft. The S3b domain binds preferentially to undertwisted segions of collagen.
Sequence:
MKKNILKILMDSYSKESKIQTVRRVTSVSLLAVYLTMNTSSLVLAKPIENTNDTSIKNVEKLRNAPNEENSKKVEDSKNDKVEHVKNIEEAKVEQVAPEVKSKSTLRSASIANTNSEKYDFEYLNGLSYTELTNLIKNIKWNQINGLFNYSTGSQKFFGDKNRVQAIINALQESGRTYTANDMKGIETFTEVLRAGFYLGYYNDGLSYLNDRNFQDKCIPAMIAIQKNPNFKLGTAVQDEVITSLGKLIGNASANAEVVNNCVPVLKQFRENLNQYAPDYVKGTAVNELIKGIEFDFSGAAYEKDVKTMPWYGKIDPFINELKALGLYGNITSATEWASDVGIYYLSKFGLYSTNRNDIVQSLEKAVDMYKYGKIAFVAMERITWDYDGIGSNGKKVDHDKFLDDAEKHYLPKTYTFDNGTFIIRAGDKVSEEKIKRLYWASREVKSQFHRVVGNDKALEVGNADDVLTMKIFNSPEEYKFNTNINGVSTDNGGLYIEPRGTFYTYERTPQQSIFSLEELFRHEYTHYLQARYLVDGLWGQGPFYEKNRLTWFDEGTAEFFAGSTRTSGVLPRKSILGYLAKDKVDHRYSLKKTLNSGYDDSDWMFYNYGFAVAHYLYEKDMPTFIKMNKAILNTDVKSYDEIIKKLSDDANKNTEYQNHIQELADKYQGAGIPLVSDDYLKDHGYKKASEVYSEISKAASLTNTSVTAEKSQYFNTFTLRGTYTGETSKGEFKDWDEMSKKLDGTLESLAKNSWSGYKTLTAYFTNYRVTSDNKVQYDVVFHGVLTDNADISNNKAPIAKVTGPSTGAVGRNIEFSGKDSKDEDGKIVSYDWDFGDGATSRGKNSVHAYKKAGTYNVTLKVTDDKGATATESFTIEIKNEDTTTPITKEMEPNDDIKEANGPIVEGVTVKGDLNGSDDADTFYFDVKEDGDVTIELPYSGSSNFTWLVYKEGDDQNHIASGIDKNNSKVGTFKSTKGRHYVFIYKHDSASNISYSLNIKGLGNEKLKEKENNDSSDKATVIPNFNTTMQGSLLGDDSRDYYSFEVKEEGEVNIELDKKDEFGVTWTLHPESNINDRITYGQVDGNKVSNKVKLRPGKYYLLVYKYSGSGNYELRVNK