Complement Factor H Related Protein 4 (CFHR4)

The deduced 331-amino acid protein contains a potential 19-amino acid signal peptide, 4 potential N-linked glycosylation sites, and 5 SCRs. The CFHR4 SCRs share sequence identities of 63 to 70% with those of CFH, except for SCR 5, which is only 39% identical to SCR 20 of CFH.

The CFHR4 C-terminal SCRs are over 93% identical to those of CFHR3. Northern blot analysis of liver RNA revealed expression of 1.4-, 2.2-, and 2.5-kb transcripts, with the shorter transcript predicted to be CFHR4 specific. Western blot analysis showed that CFHR4 in serum is an 86-kD dimeric protein and a 63-kD monomeric protein after extensive reducing treatment, whereas the recombinant proteins are 84 kD and 42 kD, suggesting that the difference is due to carbohydrate attachment.