An intronless gene encoding a potential member of the family of receptors coupled to guanine nucleotide regulatory proteins

Plasma membrane receptors for hormones, drugs, neurotransmit-ters and sensory stimuli are coupled to guanine nucleotide regulatory proteins. Recent cloning of the genes and/or cDNAs for several of these receptors including the visual pigment rhodopsin¹, the adenylate-cyclase stimulatory β-adrenergic receptor^2-4 and two subtypes of muscarinic cholinergic receptors^5,6 has suggested that these are homologous proteins with several conserved structural and functional features. Whereas the rhodopsin gene consists of five exons interrupted by four introns¹, surprisingly the human and hamster β-adrenergic receptor genes contain no introns in either their coding or untranslated sequences⁷. We have cloned and sequenced a DNA fragment in the human genome which cross-hybridizes with a full-length β₂-adrenergic receptor probe at reduced stringency. Like the β₂-adrenergic receptor this gene appears to be intronless, containing an uninterrupted long open reading frame which encodes a putative protein with all the expected structural features of a G-protein-coupled receptor.