首页>
外文期刊>journal of cellular biochemistry
>Activating mutations in the NH2‐ and COOH‐terminal moieties of the Gsα subunit have dominant phenotypes and distinguishable kinetics of adenylyl cyclase stimulation
【24h】
Activating mutations in the NH2‐ and COOH‐terminal moieties of the Gsα subunit have dominant phenotypes and distinguishable kinetics of adenylyl cyclase stimulation
展开▼
机译：Activating mutations in the NH2‐ and COOH‐terminal moieties of the Gsα subunit have dominant phenotypes and distinguishable kinetics of adenylyl cyclase stimulation
AbstractThe α subunit polypeptides of the G proteins Gsand Gi2stimulate and inhibit adenylyl cyclase, respectively. The αsand αi2subunits are 65 homologous in amino acid sequence but have highly conserved GDP/GTP binding domains. Previously, we mapped the functional adenylyl cyclase activation domain to a 122 amino acid region in the COOH‐terminal moiety of the αspolypeptide (Osawa et al: Cell 63:697–706, 1990). The NH2‐terminal half of the αspolypeptide encodes domains regulating βγ interactions and GDP dissociation. A series of chimeric cDNAs having different lengths of the NH2‐or COOH‐terminal coding sequence of αssubstituted with the corresponding αi2sequence were used to introduce multi‐residue non‐conserved mutations in different domains of the αspolypeptide. Mutation of either the amino‐ or carboxy‐terminus results in an αspolypeptide which constitutively activates cAMP synthesis when expressed in Chinese hamster ovary cells. The activated αspolypeptides having mutations in either the NH2‐ or COOH‐terminus demonstrate an enhanced rate of GTPγS activation of adenylyl cyclase. In membrane preparations from cells expressing the various αsmutants, COOH‐terminal mutants, but not NH2‐terminal αsmutants markedly enhance the maximal stimulation of adenylyl cyclase by GTPγS and fluoride ion. Neither mutation at the NH2‐ nor COOH‐terminus had an effect on the GTPase activity of the αspolypeptides. Thus, mutation at NH2‐and COOH‐termini influence the rate of αsactivation, but only the COOH‐terminus appears to be involved in the regulation of the αspolypeptide
展开▼
