properdin properdin properdin is protein that in humans is encoded by the cfp (complement factor properdin) gene. cfpavailable structurespdbortholog search: pdbe rcsb list of pdb id codes1w0r, 1w0sidentifiersaliasescfp, bfd, pfc, pfd, properdin, complement factor properdin, properdinexternal idsomim: 300383 mgi: 97545 homologene: 1969 genecards: cfp gene location (human)chr.x chromosome (human)bandxp11.23start47,623,172 bpend47,630,305 bpgene location (mouse)chr.x chromosome (mouse)bandx a1.3|x 16.44 cmstart20,791,693 bpend20,797,794 bprna expression patternbgeehumanmouse (ortholog)top expressed inmonocytebloodspleenbone marrowbone marrow cellsappendixlymph noderight lungliverright lobe of livertop expressed inspleenankle jointright lobe of liveraxillary lymph nodewhite adipose tissuethymuslipsubcutaneous adipose tissuebloodascending aortamore reference expression databiogpsn/agene ontologymolecular function protein binding serine-type endopeptidase activity cellular component extracellular matrix endoplasmic reticulum lumen extracellular region extracellular space specific granule lumen tertiary granule lumen collagen-containing extracellular matrix biological process immune response regulation of complement activation defense response to bacterium immune system process complement activation protein o-linked fucosylation complement activation, alternative pathway innate immune response neutrophil degranulation proteolysis sources:amigo / quickgoorthologsspecieshumanmouseentrez519918636ensemblensg00000126759ensmusg00000001128uniprotp27918p11680refseq (mrna)nm_002621nm_001145252nm_008823refseq (protein)np_001138724np_002612np_032849location (ucsc)chr x: 47.62 – 47.63 mbchr x: 20.79 – 20.8 mbpubmed searchwikidataview/edit humanview/edit mouse properdin is plasma glycoprotein that activates the complement system of the innate immune system. this protein binds to bacterial cell walls and dying human cells to stabilize the c3 and c5-convertase enzyme complexes to form an attack complex that lead to the lysis of the cell. structure properdin is a gamma globulin protein composed of multiple identical protein subunits with a separate ligand-binding site. native properdin occurs in head-to-tail dimers, trimers and tetramers in the fixed ratio 22:52:28. function it is known that it participates in some specific immune responses. it plays a part in tissue inflammation as well as the engulfing of pathogens by phagocytes. in addition it is known to help to neutralize some viruses. the properdin promotes the association of c3b with factor b and provides a focal point for the assembly of c3bbb on a surface. it binds to preformed alternative pathway c3-convertases. properdin also inhibits the factor h – mediated cleavage of c3b by factor i. alternative pathway. properdin is the "p" in the blue circles. (some labels are in polish.) the alternative pathway is not dependent on antibodies. this branch of the complement system is activated by iga immune complexes and bacterial endotoxins, polysaccharides, and cell walls, and results in producing anaphylatoxins, opsonins, chemotactic factors, and the membrane attack complex, all of which help fight pathogens. history properdin was discovered in 1954 by dr. louis pillemer of the institute of pathology (now the department of pathology at case western reserve university). deficiency properdin deficiency is a rare x-linked disease in which properdin is deficient. affected individuals are susceptible to fulminant meningococcal disease.