Enables complement component C3b binding activity and heparin binding activity. Predicted to be involved in regulation of complement activation. Located in extracellular space. Human ortholog(s) of this gene implicated in age related macular degeneration 1 and atypical hemolytic-uremic syndrome. Orthologous to several human genes including CFHR3 (complement factor H related 3). [provided by Alliance of Genome Resources, Apr 2022]