title: Alanine-23 of transducin alpha subunit is involved in defining the affinity for betagamma complex.
abstract: Transducin a subunit (alpha(t1)) shows extraordinarily high affinity to G protein beta(gamma) complex. One of the beta(gamma)-binding regions on alpha(t1) is the amino-terminal helix. Alanine-23 is uniquely found on alpha(t1) but not other members of the G(i)-subfamily. Mutation of alanine-23 into serine reduced the ability of alpha(t1) to sequester beta(gamma)-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(t1) 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(t1) is probably involved in defining its affinity for the beta(gamma) 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: D000409:Alanine; D000700:Analgesics / Q000494:pharmacology; D016375:Antisense Elements (Genetics); D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004745:Enkephalins / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000166:cytology; D008958:Models, Molecular; D016296:Mutagenesis / Q000502:physiology; D010641:Phenotype; D011487:Protein Conformation; D013268:Stimulation, Chemical; D015293:Transducin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D000700:Analgesics; D016375:Antisense Elements (Genetics); D004745:Enkephalins; C073188:enkephalin, 2,6-dimethyl-Tyr(1)-Pen(2,5)-; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D015293:Transducin; D000409:Alanine