C5: Activation of C5 by a C5 convertase initiates the spontaneous assembly of the late complement components, C5-C9, into the membrane attack complex. C5b has a transient binding site for C6. The C5b-C6 complex is the foundation upon which the lytic complex is assembled. Defects in C5 are the cause of complement component 5 deficiency (C5D). A rare defect of the complement classical pathway associated with susceptibility to severe recurrent infections, predominantly by Neisseria gonorrhoeae or Neisseria meningitidis. An association study of C5 haplotypes and genotypes in individuals with chronic hepatitis C virus infection shows that individuals homozygous for the C5_1 haplotype have a significantly higher stage of liver fibrosis than individuals carrying at least 1 other allele (PubMed:15995705).

Protein type: Secreted; Secreted, signal peptide

Cellular Component: extracellular space

Molecular Function: C5a anaphylatoxin chemotactic receptor binding

Biological Process: cellular calcium ion homeostasis; chemotaxis; glucose homeostasis; in utero embryonic development; inflammatory response; leukocyte migration during inflammatory response; negative regulation of dopamine secretion; positive regulation of angiogenesis; positive regulation of chemotaxis