Complement Factor H Related Protein 3 (CFHR3)

Human complement factor H (CFH) and the 5 factor H-related proteins, CFHR1, CFHR2, CFHR3, CFHR4 , and CFHR5, are exclusively composed of highly-related short consensus repeats (SCRs), each of which contains 4 cysteine residues and additional conserved amino acids.

The deduced 331-amino acid protein has a 19-amino acid signal peptide, 4 N-linked glycosylation sites, and 5 SCRs. SCR 1 and 2 of CFHL3 are homologous to SCR 6 and 7 of CFH, whereas SCR 3, 4, and 5 of CFHR3 are somewhat less homologous to SCR 8, 19, and 20 of CFH. Northern blot analysis revealed expression of a 1.4-kb CFHR3 transcript in liver. Autoradiographic analysis determined that CFHR3 is secreted as a 37.5-kD protein.