Complement factor I

CFI
Identifiers
Aliases	CFI, AHUS3, ARMD13, C3BINA, C3b-INA, FI, IF, KAF, complement factor I
External IDs	OMIM: 217030; MGI: 105937; GeneCards: CFI
Available structures
PDB	Ortholog search: PDBe RCSB
List of PDB id codes
	2XRC
Enzyme activity
Gene location (Human)
Chr.	Chromosome 4 (human)
End	109,802,179 bp
Gene location (Mouse)
Chr.	Chromosome 3 (mouse)
End	129,668,981 bp
RNA expression pattern
	Top expressed in
	germinal epithelium; ; parietal pleura; ; right lobe of liver; ; gallbladder; ; palpebral conjunctiva; ; visceral pleura; ; kidney tubule; ; human kidney; ; right adrenal cortex; ; caput epididymis;
	Top expressed in
	left lobe of liver; ; epithelium of stomach; ; pyloric antrum; ; gallbladder; ; mucous cell of stomach; ; fetal liver hematopoietic progenitor cell; ; migratory enteric neural crest cell; ; human fetus; ; endocardial cushion; ; yolk sac;
	More reference expression data
	n/a
Gene ontology
Molecular function	peptidase activity; hydrolase activity; serine-type peptidase activity; metal ion binding; serine-type endopeptidase activity; scavenger receptor activity; protein binding;
Cellular component	extracellular exosome; membrane; extracellular region; extracellular space;
Biological process	complement activation, classical pathway; regulation of complement activation; receptor-mediated endocytosis; proteolysis; immune system process; innate immune response; viral process; vesicle-mediated transport; endocytosis;
	Sources:Amigo / QuickGO
Orthologs
Databases	NCBI: entry; OMA: entry
	3426
	12630
	ENSG00000205403
	ENSMUSG00000058952
	P05156; Q8WW88
	Q61129
	NM_000204; NM_001318057; NM_001331035
	NM_007686; NM_001329552
NP_000195; NP_001304986; NP_001317964; NP_001362207; NP_001362208;
	NP_001362209; NP_001362210; NP_001362211; NP_001362212; NP_001362213; NP_001304986.1
	NP_001316481; NP_031712
	Wikidata
View/Edit Human	View/Edit Mouse

Complement factor I, also known as C3b/C4b inactivator, is a protein that in humans is encoded by the CFI gene. Complement factor I (factor I) is a protein of the complement system, first isolated in 1966 in guinea pig serum, that regulates complement activation by cleaving cell-bound or fluid phase C3b and C4b. It is a soluble glycoprotein that circulates in human blood at an average concentration of 35 μg/mL.