Receptor for ADP and ATP coupled to G-proteins that inhibit the adenylyl cyclase second messenger system. Not activated by UDP and UTP. Required for normal platelet aggregation and blood coagulation. Highly expressed in the platelets, lower levels in the brain. Lowest levels in the lung, appendix, pituitary and adrenal gland. Expressed in the spinal cord and in the fetal brain. The transmembrane domain is composed of seven transmembrane helices; most of these are not strictly perpendicular to the plane of the membrane, but are tilted and/or kinked. Agonist binding promotes a conformation change in the extracellular loops that leads to an inward movement of the transmembrane helices. Antagonists such as AZD1283 can bind to an overlapping site, but block the inward movement of the transmembrane helices (PubMed:24670650, PubMed:24784220). The disease is caused by variants affecting the gene represented in this entry. Belongs to the G-protein coupled receptor 1 family.