The reference OMIM entry for this protein is 300383

Complement factor properdin; cfp
Properdin p factor, complement; pfc
Properdin
Factor p

DESCRIPTION

Properdin (factor P) is a plasma protein that is active in the alternative complement pathway of the innate immune system. It is a positive regulatory factor that binds to many microbial surfaces to stabilize the C3b,Bb convertase. The C3b,Bb convertase then rapidly cleaves more C3 to C3b, which acts either as an opsonin or to reinitiate the pathway in an amplification loop that proceeds on the bacterial cell, but not on the host cell (Janeway et al., 2001). In the alternative pathway, C3 is thus activated through factor B, factor D, and properdin P, under the control of factors I and H (Fearon and Austen, 1980). Deficiency of properdin is associated in particular with a heightened susceptibility to Neisseria species (Janeway et al., 2001).

MAPPING

The deficiency state of properdin (CFPD; 312060) in humans led to the identification and mapping of the properdin gene. Goundis et al. (1989) used a genomic clone of properdin for hybridization to a panel of DNA from somatic cell hybrids retaining different portions of the human X chromosome and localized the gene to Xp11.4-cen. Furthermore, in situ hybridization using the same probe refined the localization to Xp21.1-p11.23. In a restudy of a Tunisian Jewish family studied by Schlesinger et al. (1990), Ash et al. (1994) found linkage to DXS7 and one recombinant with DXS255, which had been found by Wadelius et al. (1992) to be tightly linked to properdin deficiency. Coleman et al. (1991) used a CA repeat found within 16 kb of the PFC gene to map the locus in CEPH families. The likely order was Xpter--MAOA--PFC--TIMP--Xcen. This places PFC in the region Xp11.3-p11.23. PFC and TIMP were found to be located on the same 100 kb DNA fragment. By detailed restriction mapping, Derry and Barnard (1992) showed that the properdin gene lies within 5 kb of the 5-prime end of the synapsin I gene (313440). Evans et al. (1989) mapped the properdin locus to a specific region of the mouse X chromosome by in situ hybridization. In addition to the major site of hybridization in a position predicted by the mapping of the homologous human locus to Xp21.1-p11.23, a second site of hybridization was observed. Laval et al. (1991) showed that in the mouse the Timp locus (305370) could not be separated from the properdin factor in a panel of 18 recombinant animals. The 2 loci mapped between monoamine oxidase-A and Hprt.

GENE STRUCTURE

Nolan et al. (1992) found that the PFC gene contains 10 exons and spans approximately 6 kb.

MOLECULAR GENETICS

Westberg et al. (1995) used direct solid-phase sequencing of the gene to identify point mutations in type I and type II properdin deficiency defined as absent or low serum properdin, respectively. In a Dutch family, Fredrikson et al. (1996) identified a mutation in type III properdin deficiency, defined as the presence of a dysfunctional properdin protein in serum. In 10 Dutch families, van den Bogaard et al. (2000) identified the genetic defect responsible for properdin type I deficiency. All amino acid substitutions were limited to conserved amino acids in exons 7 and 8, in contrast to premature stops that were found in other exons. Missense mutations may alter the protein conformation in such a way that properdin will not be secreted and therefore catabolized intracellularly. The decreased properdin levels found in some healthy females carrying 1 mutated properdin gene were studied for X inactivation. Most carriers with ex ... More on the omim web site

Subscribe to this protein entry history

June 30, 2020: Protein entry updated
Automatic update: OMIM entry 300383 was added.

March 3, 2020: 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).