title: The fourth intracellular domain of G-protein coupling receptors: helicity, basicity and similarity to opsins.
abstract: The minimal size of the fourth intracellular domain of heptahelical G-protein coupling receptors (GPCRs) is close to 15 residues, and a juxtamembrane 15-residue segment is predicted as helical (Helix-8) in most of the receptors. Sequences of opsins, non-visual opsin-like (family A) GPCRs and Taste-2 receptors correspond with bovine rhodopsin at four positions in this tract. This is especially evident in monoamine receptors. In most GPCRs, the conserved juxtamembrane segment also has a large fraction of basic sidechains, and a considerable excess of cationic over anionic residues. The conservation is not dependent on the preferred G-protein alpha subunit or the overall length of the domain, indicating an additive speciation. In rod opsins and some A-GPCRs this segment has been shown to associate with the bilayer and to interact with G-proteins. The segment could also be involved in precoupling of receptors and transducers. These interactions could be helped by both the structural propensities and the high content of cationic sidechains.
authors: Department of Molecular Cell Sciences, University of Memphis, Memphis, TN 38152, USA.
authors: Michael S
authors: MS
authors: Parker
authors: Steven L
authors: SL
authors: Parker
mesh_terms: D000818:Animals; D002417:Cattle; D006801:Humans; D008969:Molecular Sequence Data; D055355:Opsins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D055355:Opsins; D043562:Receptors, G-Protein-Coupled