Complement factor H-related protein 2 (CFHR2) is a C3b and heparin binding protein

摘要

Complement factor H-related protein 2 (CFHR2) is a modular protein composed of four short consensus repeats (SCR) domains and is a member of the complement factor H protein family with so far unknown function(s). The N-terminal two SCRs of CFHR2 show almost sequence identity to the C5 binding region of the terminal pathway regulator CFHR1. Similarly the C-terminal two SCRs of CFHR2 show a high level of amino acid identity to the recognition site of factor H, the main regulator of the alternative complement pathway. This homology suggests similar activities among the related proteins. Here we demonstrate that recombinant CFHR2, like factor H, binds to the central complement component C3b as well as to heparin. Based on this related binding we hypothesize that CFHR2 by binding to C3b on self surfaces does inhibit local complement activation and contributes to homeostasis.