Receptor for the chemotactic and inflammatory peptide anaphylatoxin C5a. The ligand interacts with at least two sites on the receptor: a high-affinity site on the extracellular N-terminus, and a second site in the transmembrane region which activates downstream signaling events. Receptor activation stimulates chemotaxis, granule enzyme release, intracellular calcium release and superoxide anion production. C5AR1 Protein, Human, Recombinant (Cell-Free, His) is expressed in E. coli expression system with C-10xHis tag. The predicted molecular weight is 40.7 kDa and the accession number is P21730.