title: Alanine-23 of transducin alpha subunit is involved in defining the affinity for betagammma complex.
abstract: Transducin alpha subunit (alpha(t)1) shows extraordinarily high affinity to G protein betagamma complex. One of the betagamma-binding regions on alphat1 is the amino-terminal helix. Alanine-23 is uniquely found on alphat1 but not other members of the Gi-subfamily. Mutation of alanine-23 into serine reduced the ability of alpha(t)1 to sequester betagamma-mediated stimulation of type II adenylyl cyclase. The functional impairment is independent to the protein expression levels. Molecular modeling indicated that the hydrophobic interaction between the side chains of alanine-23 of alpha(t)1 and leucine-55 of the beta1 subunit could be disrupted by the introduction of a hydroxyl group. This study showed that alanine-23 of alpha(t)1 is probably involved in defining its affinity for the betagamma complex.
authors.affiliation: Department of Biology, Hong Kong University of Science and Technology, Kowloon, China.
authors.forename: M K
authors.initials: MK
authors.lastname: Ho
authors.forename: Y H
authors.initials: YH
authors.lastname: Wong
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000409:Alanine / Q000737:chemistry*; D019943:Amino Acid Substitution; D002460:Cell Line; D019204:GTP-Binding Proteins / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry*; D012694:Serine / Q000737:chemistry; D013268:Stimulation, Chemical; D015293:Transducin / Q000737:chemistry*
chemical_list: D010446:Peptide Fragments; D012694:Serine; D019204:GTP-Binding Proteins; D015293:Transducin; D000262:Adenylyl Cyclases; D000409:Alanine