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. In inbred mouse strains there are at least 6 alleles that can occur at the HBA locus: A, B, C, D, F, or G. Strains carrying the A and F alleles produce a single kind of alpha chain, whereas those carrying B, C, D, or G each produce 2 kinds of chains. The sequence shown is that of the B(1) and D(1) allele chains. Belongs to the globin family.