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Protein Page:
C3 (human)

C3 C3 plays a central role in the activation of the complement system. Its processing by C3 convertase is the central reaction in both classical and alternative complement pathways. After activation C3b can bind covalently, via its reactive thioester, to cell surface carbohydrates or immune aggregates. Defects in C3 are the cause of complement component 3 deficiency (C3D). A rare defect of the complement classical pathway. Patients develop recurrent, severe, pyogenic infections because of ineffective opsonization of pathogens. Some patients may also develop autoimmune disorders, such as arthralgia and vasculitic rashes, lupus-like syndrome and membranoproliferative glomerulonephritis. Genetic variation in C3 is associated with susceptibility to age-related macular degeneration type 9 (ARMD9). ARMD is a multifactorial eye disease and the most common cause of irreversible vision loss in the developed world. In most patients, the disease is manifest as ophthalmoscopically visible yellowish accumulations of protein and lipid that lie beneath the retinal pigment epithelium and within an elastin- containing structure known as Bruch membrane. Defects in C3 are a cause of susceptibility to hemolytic uremic syndrome atypical type 5 (AHUS5). An atypical form of hemolytic uremic syndrome. It is a complex genetic disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, renal failure and absence of episodes of enterocolitis and diarrhea. In contrast to typical hemolytic uremic syndrome, atypical forms have a poorer prognosis, with higher death rates and frequent progression to end-stage renal disease. Susceptibility to the development of atypical hemolytic uremic syndrome can be conferred by mutations in various components of or regulatory factors in the complement cascade system. Other genes may play a role in modifying the phenotype. Increased levels of C3 and its cleavage product ASP, are associated with obesity, diabetes and coronary heart disease. Short-term endurance training reduces baseline ASP levels and subsequently fat storage. Note: This description may include information from UniProtKB.
Protein type: Inhibitor; Secreted; Secreted, signal peptide
Chromosomal Location of Human Ortholog: 19p13.3-p13.2
Cellular Component: extracellular region; extracellular space; plasma membrane
Molecular Function: C5L2 anaphylatoxin chemotactic receptor binding; protein binding; receptor binding; serine-type endopeptidase activity
Biological Process: complement activation; complement activation, alternative pathway; G-protein coupled receptor protein signaling pathway; immune response; positive regulation of G-protein coupled receptor protein signaling pathway; positive regulation of protein amino acid phosphorylation; regulation of complement activation; regulation of immune response; signal transduction
Disease: Complement Component 3 Deficiency, Autosomal Recessive; Hemolytic Uremic Syndrome, Atypical, Susceptibility To, 5; Macular Degeneration, Age-related, 9
Reference #:  P01024 (UniProtKB)
Alt. Names/Synonyms: acylation-stimulating protein cleavage product; AHUS5; ARMD9; C3; C3 and PZP-like alpha-2-macroglobulin domain-containing protein 1; C3a anaphylatoxin; CO3; Complement C3; Complement C3 alpha chain; Complement C3 beta chain; Complement C3b alpha' chain; Complement C3c alpha' chain fragment 1; Complement C3c alpha' chain fragment 2; Complement C3d fragment; Complement C3dg fragment; Complement C3f fragment; Complement C3g fragment; complement component 3; complement component C3; CPAMD1
Gene Symbols: C3
Molecular weight: 187,148 Da
Basal Isoelectric point: 6.02  Predict pI for various phosphorylation states
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