Involved in oxygen transport from the lung to the various peripheral tissues. Hemopressin acts as an antagonist peptide of the cannabinoid receptor CNR1. Hemopressin-binding efficiently blocks cannabinoid receptor CNR1 and subsequent signaling. Heterotetramer of two alpha chains and two beta chains. Red blood cells. The sequence shown is one of two non-allelic alpha chains from dog. Belongs to the globin family.