Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.12 (PKG)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bovine lung cGMP-binding cGMP-specific phosphodiesterase (cG-BPDE) is a potent and relatively specific substrate for cGMP-dependent protein kinase (cGK) as compared to cAMP-dependent protein kinase (cAK) (Thomas, M. K., Francis, S. H., and Corbin, J. D. (1990) J. Biol. Chem. 265, 14971-14978). A synthetic peptide, RKISASEFDRPLR (BPDEtide), was synthesized corresponding to the sequence surrounding the phosphorylation site in cG-BPDE. BPDEtide retained the cGK/cAK kinase specificity demonstrated by native cG-BPDE: the apparent Km of BPDEtide for cGK was 5-fold lower than that for cAK (Km = 68 and 320 microM, respectively). Vmax values were 11 mumol/min/mg for cGK and 3.2 mumol/min/mg for cAK. The peptide was not phosphorylated to a measurable extent by protein kinase C or by calcium/calmodulin-dependent protein kinase II. Thus, the primary amino acid sequence of the peptide substrate was sufficient to confer kinase specificity. Studies in crude tissue extracts indicated that BPDEtide was the most selective peptide substrate documented for measuring cGK activity. Peptide analogs of BPDEtide were synthesized to determine the contribution of specific residues to cGK or cAK substrate specificity. Substitution of a Lys for the amino-terminal Arg did not reduce cGK/cAK specificity; neither did the exchange of an Ala for the non-phosphorylated Ser nor the removal of the 3 carboxyl-terminal residues. A truncated BPDEtide (RKISASE) served equally well as substrate (Km approximately 90 microM) for both kinases. However, restoration of the Phe, to yield RKISASEF, reproduced the original cGK/cAK specificity for BPDEtide (Km = 120 and 480 microM, respectively), primarily by decreasing the affinity of cAK. Addition of a carboxyl-terminal Phe to the peptide RKRSRAE (derived from the sequence of the cGK phosphorylation site in histone H2B) or to the peptide LRRASLG (derived from the sequence of the cAK phosphorylation site in pyruvate kinase) also improved the cGK/cAK specificity by decreasing the affinity of cAK. These data suggested that the Phe in each substrate tested is a negative determinant for cAK.
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PMID:A phenylalanine in peptide substrates provides for selectivity between cGMP- and cAMP-dependent protein kinases. 131 60

We recently described a novel isozyme of cGMP-dependent protein kinase (type I beta). It has a structure and peptide substrate specificity which is similar to that of type I alpha, but it has a different cGMP binding behavior, and autophosphorylation occurs almost entirely in serine instead of in both serine and threonine residues (Wolfe, L., Corbin, J.D., and Francis, S.H. (1989) J. Biol. Chem. 264, 7734-7741). An amino-terminal sequence of 31 amino acids derived from three proteolytic fragments of type I beta had 45% homology with a sequence beginning at type I alpha-47. However, sequences of three CNBr peptides of type I beta were identical to sequences of type I alpha beginning at type I alpha-202, -213, and -576 of 11, 27, and 30 residues. These sequences include portions of the catalytic domain and at least one cGMP-binding domain (site 1). Thus, types I alpha and I beta may be produced by alternative splicing of two unique mRNA segments to generate different amino acid sequences in the protein in a region that is amino-terminal to type I alpha-202. This segment in type I beta corresponds to the region in type I alpha that includes the major autophosphorylation site (Thr-58) which is within the domain that is proposed to inhibit catalytic activity. This region presumably interacts with the cGMP-binding site(s) to account for the differences in cGMP-binding behavior between types I alpha and I beta. Even though the sequence of type I beta in the variable region lacks the residue corresponding to Thr-58, it includes a consensus phosphorylation site (KRQAISA) beginning at type I alpha-59, which is absent in type I alpha. The results imply flexibility in the design of the autophosphorylation site and, hence, of the inhibitory domain.
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PMID:Types I alpha and I beta isozymes of cGMP-dependent protein kinase: alternative mRNA splicing may produce different inhibitory domains. 327 99

Although the cAMP-dependent (PKA) and cGMP-dependent protein kinases (PKG) usually participate in unrelated biological processes, their enzymological properties are decidedly similar. Based upon the multitude of comparative studies conducted to date, it appears that these two enzymes exhibit very similar peptide substrate specificities. Furthermore, most inhibitors that have been reported for PKG serve in a nearly equal capacity for PKA. Consequently, the task of distinguishing between these enzymes, especially under in vivo conditions, has proved to be daunting. However, we have recently found that PKA will only phosphorylate non-amino acid residues whose alpha-configuration corresponds to that found in L-amino acids, whereas PKG will catalyze the phosphorylation of residues corresponding to both L- and D-amino acids (Wood, J., Mendelow, M., Yan, X., Corbin, J.D., Francis, S.H., and Lawrence, D.S. (1996) J. Biol. Chem. 271, 174-179). Based on these results, we have designed a potent affinity label for PKG (KI = 21.1 +/- 4.7 microM), that has no measurable activity toward PKA. This represents the first example of an peptide-based inactivator that fully distinguishes between these two closely related enzymes. These results suggest that a similar strategy may provide highly specific inactivators for other protein kinases as well.
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PMID:Precision targeting of protein kinases. An affinity label that inactivates the cGMP- but not the cAMP-dependent protein kinase. 856 27

Binding of cyclic nucleotide to or autophosphorylation of cGMP-dependent protein kinase (PKG) activates this kinase, but the molecular mechanism of activation for either process is unknown. Activation of PKG by cGMP binding produces a conformational change in the enzyme (Chu, D.-M., Corbin, J. D., Grimes, K. A., and Francis, S. H. (1997) J. Biol. Chem. 272, 31922-31928; Zhao, J., Trewhella, J., Corbin, J., Francis, S., Mitchell, R., Brushia, R., and Walsh, D. (1997) J. Biol. Chem. 272, 39129-31936). In the present studies, activation of type Ibeta PKG by either autophosphorylation or cGMP-binding alone causes (i) an electronegative charge shift on ion exchange chromatography, (ii) a similar increase ( approximately 3.5 A) in the Stokes radius as determined by gel filtration chromatography, and (iii) a similar decrease in the mobility of the enzyme on native gel electrophoresis. Consistent with these results, cGMP binding increases the rate of phosphoprotein phosphatase-1 catalyzed dephosphorylation of PKG which is autophosphorylated only at Ser-63 (not activated); however, dephosphorylation of PKG that is highly autophosphorylated (activated) is not stimulated by cGMP. The combined results suggest that activation of PKG by either autophosphorylation or cGMP binding alone produces a similar apparent elongation of the enzyme, implying that either process activates the enzyme by a similar molecular mechanism.
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PMID:Activation by autophosphorylation or cGMP binding produces a similar apparent conformational change in cGMP-dependent protein kinase. 960 83

In addition to its cGMP-selective catalytic site, cGMP-binding cGMP-specific phosphodiesterase (PDE5) contains two allosteric cGMP-binding sites and at least one phosphorylation site (Ser92) on each subunit [Thomas, M.K., Francis, S.H. & Corbin, J.D. (1990) J. Biol. Chem. 265, 14971-14978]. In the present study, prior incubation of recombinant bovine PDE5 with a phosphorylation reaction mixture [cGMP-dependent protein kinase (PKG) or catalytic subunit of cAMP-dependent protein kinase (PKA), MgATP, cGMP, 3-isobutyl-1-methylxanthine], shown earlier to produce Ser92 phosphorylation, caused a 50-70% increase in enzyme activity and also increased the affinity of cGMP binding to the allosteric cGMP-binding sites. Both effects were associated with increases in its phosphate content up to 0.6 mol per PDE5 subunit. Omission of any one of the preincubation components caused loss of stimulation of catalytic activity. Addition of the phosphorylation reaction mixture to a crude bovine lung extract, which contains PDE5, also produced a significant increase in cGMP PDE catalytic activity. The increase in recombinant PDE5 catalytic activity brought about by phosphorylation was time-dependent and was obtained with 0.2-0.5 microM PKG subunit, which is approximately the cellular level of this enzyme in vascular smooth muscle. Significantly greater stimulation was observed using cGMP substrate concentrations below the Km value for PDE5, although stimulation was also seen at high cGMP concentrations. Considerably higher concentration of the catalytic subunit of PKA than of PKG was required for activation. There was no detectable difference between phosphorylated and unphosphorylated PDE5 in median inhibitory concentration for the PDE5 inhibitors, sildenafil, or zaprinast 3-isobutyl-1-methylxanthine. Phosphorylation reduced the cGMP concentration required for half-maximum binding to the allosteric cGMP-binding sites from 0.13 to 0.03 microM. The mechanism by which phosphorylation of PDE5 by PKG could be involved in physiological negative-feedback regulation of cGMP levels is discussed.
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PMID:Phosphorylation of phosphodiesterase-5 by cyclic nucleotide-dependent protein kinase alters its catalytic and allosteric cGMP-binding activities. 1078 99