The Duffy blood group system consists of five antigens carried on a multipass membrane glycoprotein called the Atypical Chemokine Receptor 1 (ACKR1), CD234 (previously known as Duffy Antigen Receptor for Chemokines: DARC). It consists of 336 (major) and 338 (minor) amino acids. The major transcript is derived from exon 1 and exon 2 of ACKR1; the minor product is a transcript initiated at the beginning of exon 2. The amino terminus is predicted to be extracellular and the carboxyl terminus intracellular.