Guanosine triphosphate-activating proteins

Synthesized by soluble guanylyl cyclase and particulate guanylyl cyclase from guanosine triphosphate (GTP). Nitric oxide activates soluble guanylyl cyclase to enhance cyclic GMP production that contributes to various NO actions. Cyclic GMP is hydrolyzed by phosphodiesterases. Cyclic GMP binds to and activates cGMP-dependent protein kinase, phosphodiesterases, and Cyclic Nucleotide-regulated Cation Channels. 

The activated receptor combines with the G-protein in its Ggdp form, with the consequence that guanosine triphosphate (GTP) can replace previously bound guanosine diphosphate (GDP). The extent to which this can occur will be influenced by the local concentration of GTP. 

G proteins comprise several families of diverse cellular proteins that subserve an equally diverse array of cellular functions. These proteins derive their name from the fact that they bind the guanine nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP) and possess intrinsic GTPase activity. G proteins play a central role in signal transduction as well as in a myriad of cellular processes, including membrane vesicle transport,... 

There are several intracellular second messengers that are activated by metabotropic receptors, also referred to as G protein-coupled receptors (Duman and Nestler 1999). These receptors couple with G proteins that are heterotrimers made up of a-, (3- and y-subunits. Interaction of the G protein heterotrimer with activated receptor increases the exchange of guanosine triphosphate (GTP) for bound guanosine diphosphate (GDP), resulting in dissociation of the heterotrimer into free a and (3y subunits that in turn can regulate second messen-... 

Schweins, T., Geyer, M., Kalbitzer, H. R., Wittinghofer, A., and Warshel, A. (1996). Linear free energy relationships in the intrinsic and GTPase activating protein-stimulated guanosine 5 -triphosphate hydrolysis of p21ras. Biochemistry 35, 14225-14231. 

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