3.4.21.41: complement subcomponent C1r
This is an abbreviated version!
For detailed information about complement subcomponent C1r, go to the full flat file.
Reaction
Selective cleavage of Lys(or Arg)-/-Ile bond in complement subcomponent C1s to form C_overbar_1s_ (EC 3.4.21.42) =
Synonyms
activated complement C1r, C1r, C1r protease, C1r serine protease, C1r-LP, C1rbar-esterase, complement C1r subcomponent-like protein, complement C1r, activated, complement protease C1r, complement subcomponent 1r, CUB, multiprotein complex C1, proteases C1r, serine protease C1r, Xld, xolloid
ECTree
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Subunits
Subunits on EC 3.4.21.41 - complement subcomponent C1r
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dimer
additional information
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x * 69500, enzyme fused to maltose binding protein, SDS-PAGE
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2 * 83000, SDS-PAGE of reduced protein, gel filtration in 6 M guanidinium hydrochloride
dimer
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2 * 85000, the C1rbar subunits consist of one polypeptide chain of 56000 Da, A-chain, that is disulfide-linked to a 27000 Da B-chain, SDS-PAGE
dimer
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CCP1 is essential to the assembly of the dimer, but formation of a stable dimer is not a prerequisite for self-activation
dimer
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deletion of CCP1 domain from CCP1-CCP2-SP fragment results in the loss of the dimeric structure. Dimerization of C1r is not a prerequisite for autoactivation
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the C1 complex comprises two loosely interacting subunits, C1q and the Ca2+-dependent C1s-C1r-C1r-C1s tetramer. Binding of C1 to activator is mediated by C1q and triggers activation of proenzyme C1r into an active protease C1rbar, which in turn activates C1s, thereby initiating the classical pathway of complement
additional information
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on activation the single polypeptide chain of C1r is cleaved probably at a single position, the C1rbar subunits consist of 1 polypeptide chain of 56000 Da, A-chain, that is disulfide-linked to a 27000 Da B-chain
additional information
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C1rbar and the proenzyme C1r are noncovalent dimers, the subunit of C1r has a MW of 53000-85000 Da, SDS-PAGE
additional information
C1r and C1s pro-enzymes form a heterotetrameric structure that associates with the recognition molecule, C1q, in the C1 complex
additional information
each C1r monomer consists of six domains, CUB1-EGF-CUB2-CCP1-CCP2-SP, i.e. an N-terminal CUB module, an EGF-like module, a second CUB module, two complement control modules CCP, and a serine protease domain SP. The three domains that constitute the catalytic fragment of C1r (CCP1-CCP2-SP) readily form head-to-tail dimers. The CUB1-EGF-CUB2 fragments of C1r also dimerize