Recombinant Human Complement Factor H-related 1 His-tag, CF

Complement factor H-related protein 1 (CFHR1) is a ~40 kDa secreted, primarily homodimeric member of the factor H family of glycoproteins (1). CFHR1 is produced by hepatocytes and circulates as two differentially glycosylated isoforms. The human complement factor H protein family consists of the complement and immune regulators factor H, the factor H-like protein 1 (FHL-1) and five factor H-related proteins (FHR-1 to -5) (2). The genes of this family are located on human chromosome 1q32, which is known as the regulator of complement activation (RCA) gene clusters (3). CFHRs are exclusively composed of individually folded protein domains, termed short consensus repeats (SCRs) or complement control modules. CFHR1 contains 5 SCRs. Although they are considered group 1 CFHRs based on conserved N-termini (2), compared to CFHR1, human CFHR2 and CFHR5 show 67.5% and 34.5% aa identity, respectively. All CFHRs, including CHFR1, are capable of binding complement factor C3b, discriminate between self and non-self cell surfaces, and have been proposed to deregulate complement activation by inhibiting interaction of CFH with C3b (2). CFHR1 inhibits complement C5 convertase activity (4). A common CFHR1/CFHR3 genetic deletion has been implicated as being protective against age-related macular degeneration (5) and nephropathy (6).  The same deletion is associated with development of factor H auto-antibodies and susceptibility to atypical hemolytic uremic syndrome due to the deletion of CFHR1 (7-8). Additionally, CFHR1 is recruited to the surface of pathogens which is suggested to result in evasion of host complement attack (9).