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MGP000358

UniProt Annotations

Entry Information
Gene Namecomplement component 4 binding protein, alpha
Protein EntryC4BPA_HUMAN
UniProt IDP04003
SpeciesHuman
Comments
Comment typeDescription
CautionIt is uncertain whether Met-1 or Met-17 is the initiator. {ECO:0000305}.
FunctionControls the classical pathway of complement activation. It binds as a cofactor to C3b/C4b inactivator (C3bINA), which then hydrolyzes the complement fragment C4b. It also accelerates the degradation of the C4bC2a complex (C3 convertase) by dissociating the complement fragment C2a. Alpha chain binds C4b. It interacts also with anticoagulant protein S and with serum amyloid P component.
InteractionP13050:arp4 (xeno); NbExp=5; IntAct=EBI-978348, EBI-978341;
SimilarityContains 8 Sushi (CCP/SCR) domains. {ECO:0000255|PROSITE-ProRule:PRU00302}.
Subcellular LocationSecreted.
SubunitDisulfide-linked complex of alpha and beta chains of 3 possible sorts: a 570 kDa complex of 7 alpha chains and 1 beta chain, a 530 kDa homoheptamer of alpha chains or a 500 kDa complex of 6 alpha chains and 1 beta chain. The central body of the alpha chain homopolymer supports tentacles, each with the binding site for C4b at the end. {ECO:0000269|PubMed:16330538}.
Tissue SpecificityChylomicrons in the plasma.
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