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. Homodimer. May also form higher-order oligomers. Interacts (when phosphorylated) with ARRB1 and ARRB2; the interaction is associated with internalization of C5aR. Interacts (via N-terminal domain) with S. aureus chemotaxis inhibitory protein (CHIPS); the interaction blocks the receptor and may thus inhibit the immune response. 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. Sulfation at Tyr-7 is important for CHIPS binding. Phosphorylated on serine residues in response to C5a binding, resulting in internalization of the receptor and short-term desensitization to C5a. Belongs to the G-protein coupled receptor 1 family.