Receptor for the chemotactic and inflammatory peptide anaphylatoxin C5a (PubMed:9464523). 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 (By similarity). Homodimer. May also form higher-order oligomers (By similarity). Interacts (when phosphorylated) with ARRB1 and ARRB2; the interaction is associated with internalization of C5aR (PubMed:12464600). Phosphorylated C5aR colocalizes with ARRB1 and ARRB2 in cytoplasmic vesicles. Sulfation plays a critical role in the association of C5aR with C5a, but no significant role in the ability of the receptor to transduce a signal and mobilize calcium in response to a small peptide agonist. Phosphorylated on serine residues in response to C5a binding, resulting in internalization of the receptor and short-term desensitization to the ligand. Belongs to the G-protein coupled receptor 1 family.