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PubMed · 6263157

Protein carboxyl-methylase modifies calmodulin function.

C Gagnon·S Kelly·V Manganiello·M Vaughn·W Strittmatter·A Hoffman·F Hirata
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3',5'-Cyclic-GMP PhosphodiesterasesAnimalsBrainCalcium-Binding ProteinsCalmodulinEnzyme ActivationKineticsProtein MethyltransferasesProtein O-MethyltransferaseJournal ArticleResearch Support, Non-U.S. Gov't

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C Gagnon, S Kelly, V Manganiello, M Vaughn, W Strittmatter, A Hoffman, F Hirata. 1980. Protein carboxyl-methylase modifies calmodulin function.. https://doi.org/10.1111/j.1749-6632.1980.tb29638.x

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Delineation of two functionally distinct gammaPDE binding sites on the bovine retinal cGMP phosphodiesterase by a mutant gammaPDE subunit.

The gamma subunit of the retinal cGMP phosphodiesterase (gammaPDE) acts as an inhibitor of phosphodiesterase (PDE) catalytic activity and mediates enzyme regulation by the alpha subunit of the GTP-binding protein transducin (alphaT). In this work, we describe a full length, doubly point-mutated gamma subunit, C68S, Y84C gammaPDE, which binds to PDE with increased affinity but has a decreased ability to inhibit the enzyme. Fluorescence studies monitoring the competition between wild-type gammaPDE and the C68S, Y84C gammaPDE mutant suggest that the mutant gammaPDE binds with high affinity to only half of the total sites occupied by wild-type gammaPDE. Competition studies between wild-type gammaPDE and the mutant further suggest that the wild-type protein is able to fully inhibit PDE activity even when the mutant gammaPDE occupies its high-affinity binding site on PDE. Taken together, our findings are consistent with a model in which there are two distinguishable binding sites for gammaPDE on the PDE enzyme but that only one of the two sites mediates PDE inhibition.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1999

Interaction sites of the C-terminal region of the cGMP phosphodiesterase inhibitory subunit with the GDP-bound transducin alpha-subunit.

In the present report, the region of interaction between the GDP-bound alpha-subunit of transducin (alphat.GTP) and the cGMP phosphodiesterase inhibitory gamma-subunit (Pgamma) has been studied. It is widely accepted that the alphat.GTP is the active form of transducin and that the GDP-bound transducin alpha-subunit (alphat. GDP) is the inactive form. We have reported previously that the binding region of the C-terminal of Pgamma on alphat.GTP is in a region between the exposed face of the alpha3 and alpha4 helices of alphat.GTP [Liu, Arshavsky and Ruoho (1996) J. Biol. Chem. 271, 26900-26907]. We now report that N-[(3-[125I]iodo-4-azidophenylpropionamido-S-(2-thiopyridyl) ]cysteine ([125I]ACTP)-derivatized Pgamma (at Cys-68) reversibly undergoes a unique disulphide exchange of the radioiodinated moiety N-(3-[125I]iodo-4-azidophenylpropionamido)cysteine ([125I]APC) from Cys-68 of Pgamma to alphat.GDP but not to the guanosine 5'-(gamma-thio)-triphosphate (GTP[S])-bound transducin alpha-subunit (alphat-GTP[S]). The specificity of the interaction was demonstrated by the fact that exchange was protected by the functionally active Cys-68-->Ala Pgamma mutant, and by pretreatment of the alphat.GDP with the betagamma-subunit of transducin. Chemical cleavage and amino acid sequencing demonstrated that the [125I]ACTP-derived Pgamma specifically transferred the [125I]APC group to Cys-250 and Cys-210 of alphat.GDP. These data indicate that the C-terminal region (especially Cys-68-Trp-70) of Pgamma interacts with alphat. GDP on the exposed interface between alpha2/beta4 and alpha3/beta5 of the alpha-subunit of transducin. Disulphide exchange was also observed with the alpha-subunit of holotransducin but this was only approx. 60% of that of pure alphat.GDP. The variation in the binding pattern between alphat.GDP and alphat.GTP with the C-terminal region of Pgamma may contribute to the functional difference between the GDP- and GTP-bound states.

3',5'-Cyclic-GMP Phosphodiesterases↗