Involved in oxygen transport from the lung to the various peripheral tissues. Hemopressin acts as an antagonist peptide of the cannabinoid receptor CNR1 (PubMed:18077343). Hemopressin-binding efficiently blocks cannabinoid receptor CNR1 and subsequent signaling (PubMed:18077343). Heterotetramer of two alpha chains and two beta chains. Red blood cells. In rats there are two non-allelic alpha chains and two non-allelic beta chains. The alpha-1 chain sequence is shown. Belongs to the globin family. PubMed:8334153 incorrectly assigned their sequence fragment as a fatty acid-binding protein.