The reference OMIM entry for this protein is 217030

Complement factor i; cfi
Complement component i
Factor i; fi
C3b inactivator

DESCRIPTION

The CFI gene encodes complement factor I ('eye'), a serine proteinase in the complement pathway responsible for cleaving and inactivating the activities of C4b (120820) and C3b (see 120700). Factor I is a plasma glycoprotein composed of 2 polypeptide chains linked by disulfide bonds. Both the light and heavy chains of factor I are encoded by the CFI gene (Catterall et al., 1987). The light chain contains the serine protease domain (Vyse et al., 1994).

CLONING

Catterall et al. (1987) isolated cDNA clones corresponding to the gene encoding complement factor I from a human liver cDNA library. The deduced 583-amino acid protein comprises both the heavy and light chains of component I, which are sequentially coded from the N terminal. The light chain N terminal is found at residue 322 after 4 basic residues, providing evidence that factor I is synthesized as a single chain polypeptide that is subsequently cleaved. Both the heavy (35.4 kD) and light (27.6 kD) chains contain 3 potential N-glycosylation sites. Northern blot analysis detected a 2.4-kb mRNA transcript. Goldberger et al. (1987) also cloned the human CFI gene.

GENE STRUCTURE

Vyse et al. (1994) determined that the CFI gene spans 63 kb and contains 13 exons, the first 8 of which encode the heavy chain and the last 5 the light chain.

MAPPING

By somatic cell hybridization, Goldberger et al. (1987) and Shiang et al. (1987) mapped the CFI gene to chromosome 4q23-q25. Shiang et al. (1989) mapped the CFI locus to 4q25 by use of somatic cell hybrids, in situ hybridization, and genetic linkage with RFLP markers. They proposed that the order of loci was as follows: cen--GC--INP10--ADH3--EGF--IF--IL2--MNS--qter. By hybridization to fragments generated by low-frequency cutting restriction enzymes and pulsed field electrophoresis, Kolble et al. (1989) showed that the CFI and EGF (131530) genes are located about 40 kb apart. The alcohol dehydrogenase cluster (103720) appeared to be more than 550 kb proximal to EGF, whereas CFI lies distal to EGF.

MOLECULAR GENETICS

Nakamura and Abe (1985) described 2 polymorphisms of the C3b inactivator gene, designated FI*A and FI*B, demonstrated by electrophoretic blotting technique. In the course of studying sera from 305 persons, Zhou and Larsen (1989) identified a third variant, designated FI*C. Data on gene frequencies of allelic variants were tabulated by Roychoudhury and Nei (1988). Ding et al. (1991) provided data on polymorphisms of the CFI gene in Chinese, Korean, and Japanese populations. - Complement Factor I Deficiency In 2 sibs with complement factor I deficiency (CFID; 610984), Vyse et al. (1996) identified a homozygous mutation in the CFI gene (217030.0001). An unrelated patient was compound heterozygous for 2 mutations in the CFI gene (217030.0001; 217030.0002). In 2 Brazilian sisters, born of consanguineous parents, with complement factor I deficiency, Baracho et al. (2003) identified a homozygous mutation in the CFI gene (217030.0003). Each parent was heterozygous for the mutation. The older sister had recurrent infections and developed systemic lupus erythematosus (SLE; 152700) with glomerulonephritis and the younger sister died at age 3 years of sepsis. Servais et al. (2007) described 2 patients with factor I deficiency who developed glomerulonephritis with isolated C3 deposits. The authors called the disorder 'glomerulonephritis C3.' The patients were found to have heterozyg ... More on the omim web site

Subscribe to this protein entry history

June 30, 2020: Protein entry updated
Automatic update: OMIM entry 217030 was added.

Jan. 21, 2019: Protein entry updated
Automatic update: Entry updated from uniprot information.

Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).