Complement C4-A (P0C0L4)

Uniprot ID P0C0L4
Protein Name Complement C4-A
Gene Name C4A
Species Homo sapiens (Human)
Signal peptide(a) N Secretome P(b) 0.398
Function Non-enzymatic component of C3 and C5 convertases and thus essential for the propagation of the classical complement pathway. Covalently binds to immunoglobulins and immune complexes and enhances the solubilization of immune aggregates and the clearance of IC through CR1 on erythrocytes. C4A isotype is responsible for effective binding to form amide bonds with immune aggregates or protein antigens, while C4B isotype catalyzes the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens.Derived from proteolytic degradation of complement C4, C4a anaphylatoxin is a mediator of local inflammatory process. It induces the contraction of smooth muscle, increases vascular permeability and causes histamine release from mast cells and basophilic leukocytes.
GO - Molecular function
  • complement component C1q complex binding : IDA:BHF-UCL
  • endopeptidase inhibitor activity : IEA:InterPro
GO - Biological process
  • cellular protein metabolic process : TAS:Reactome
  • complement activation : IGI:BHF-UCL
  • complement activation, classical pathway : IEA:UniProtKB-KW
  • inflammatory response : IEA:UniProtKB-KW
  • innate immune response : IEA:UniProtKB-KW
  • positive regulation of apoptotic cell clearance : IGI:BHF-UCL
  • post-translational protein modification : TAS:Reactome
  • regulation of complement activation : TAS:Reactome
Back
(a) The Signal peptide D-score cutoff for "YES"(having signal peptide) is 0.45.
(b) Non-classically secreted proteins should obtain an NN-score(Neural Networks score) exceeding the normal threshold of 0.5, but not at the same time be predicted to contain a signal peptide.