Zick Y, Sagi-Eisenberg R, Pines M, Gierschik P, Spiegel A M
Proc Natl Acad Sci U S A. 1986 Dec;83(24):9294-7. doi: 10.1073/pnas.83.24.9294.
The GDP-bound alpha subunit of transducin, but not the guanosine 5'-[gamma-thio]triphosphate-bound one, undergoes phosphorylation on tyrosine residues by the insulin receptor kinase and on serine residues by protein kinase C. Holotransducin is poorly phosphorylated by the insulin receptor kinase and is not phosphorylated by protein kinase C. Neither holotransducin nor any of its subunits were phosphorylated by the cAMP-dependent protein kinase. That a given subunit of transducin undergoes multisite phosphorylation depending on the type of nucleotide bound to it or the nature of the kinase suggests that hormone-dependent phosphorylation could provide a versatile mode for regulation of guanine nucleotide-binding protein (G protein) function. In particular, the findings that certain G proteins serve as substrates for both the insulin receptor kinase and protein kinase C implicate G proteins in playing a key role in mediating the action of insulin and ligands that act to activate protein kinase C.
转导素与GDP结合的α亚基可被胰岛素受体激酶磷酸化酪氨酸残基，并被蛋白激酶C磷酸化丝氨酸残基，但与鸟苷5'-[γ-硫代]三磷酸结合的α亚基则不会。全转导素被胰岛素受体激酶磷酸化的程度较低，且不会被蛋白激酶C磷酸化。全转导素及其任何亚基均不会被环磷酸腺苷依赖性蛋白激酶磷酸化。转导素的特定亚基会根据与其结合的核苷酸类型或激酶的性质进行多位点磷酸化，这表明激素依赖性磷酸化可能为调节鸟嘌呤核苷酸结合蛋白（G蛋白）功能提供一种通用模式。特别是，某些G蛋白可作为胰岛素受体激酶和蛋白激酶C的底物，这一发现表明G蛋白在介导胰岛素和激活蛋白激酶C的配体的作用中起关键作用。
