Summary

Name CFI
Full Name Complement factor I
Synonyms C3B/C4B inactivator | IF
Primary ID P05156
Links - -
Type protein
Relations 4
Function Trypsin-like serine protease that plays an essential role in regulating the immune response by controlling all complement pathways. Inhibits these pathways by cleaving three peptide bonds in the alpha-chain of C3b and two bonds in the alpha-chain of C4b thereby inactivating these proteins (PubMed:7360115, PubMed:17320177). Essential cofactors for these reactions include factor H and C4BP in the fluid phase and membrane cofactor protein/CD46 and CR1 on cell surfaces (PubMed:2141838, PubMed:9605165, PubMed:12055245). The presence of these cofactors on healthy cells allows degradation of deposited C3b by CFI in order to prevent undesired complement activation, while in apoptotic cells or microbes, the absence of such cofactors leads to C3b-mediated complement activation and subsequent opsonization (PubMed:28671664).

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Relations

Regulator Mechanism target score
+ up-regulates quantity by expression img/indirect-activation.png transcriptional regulation CFI 0.2
Publications: 1 Organism: Homo Sapiens
+ up-regulates activity img/direct-activation.png binding CFI 0.918
Publications: 1 Organism: Homo Sapiens
+ up-regulates quantity by expression img/indirect-activation.png transcriptional regulation CFI 0.2
Publications: 1 Organism: Homo Sapiens
+ down-regulates activity img/direct_inhibition.png cleavage C3 0.873
Publications: 1 Organism: Homo Sapiens
Tissue: Blood