Protein nitration

Various proteins/enzymes obtained commercially were tested for the presence of endogenously nitrated tyrosine by Western blot analysis omitting reducing agent in the step of SDS-PAGE. Histones II-S and VIII-S, IgG, cAMP-dependent protein kinase (PKA), phosphorylase b, and phosphorylase kinase exhibited strong immunoreactive bands. Histone VI-S, glycogen synthase, lactate dehydrogenase, actin, thyroglobulin, and macroglobulin exhibited moderate immunoreactivity. Histone III-S, casein, acetyl cholinesterase, DNase I, and lipase had only traceable immunoreactivity. Whereas histone VII-S, pyruvate kinase, trypsin, pepsin, chymotrypsin, protease IV, and protease XIII, and glutathione S-transferase lacked immunoreactivity. A variation of immunoreactivity between hypertensive and normaltensive rat hearts was found in the histone-agarose fractions of crude extracts. Additionally, nitrotyrosine immunoreactivity was observed in non-mammalian organisms including Eschericia coli, Saccharomyces cerevisiae and Triticum vulgaris. Upon the treatment of 15 microM peroxynitrite (PN), strong oxidant derived from nitric oxide (NO), the apparent Km of PKA for cAMP increased from approximately 10(-8) to 10(-6) M. The results imply that the varied nitration of tyrosine residues in proteins/enzymes may occur as a post-translational modification in vivo, and such discriminative nitration may be vital in PN/NO-regulated signal transduction cascade.

Denitration of peroxynitrite-treated proteins by 'protein nitratases' from rat brain and heart

Putative 'protein nitratases,' which catalyze denitration of peroxynitrite (PN)-treated proteins, were detected in the homogenate/crude extract of rat brains and hearts. Nitratase activity was monitored by the decreased intensity of nitrotyrosine immunoreactive-bands in Western blot and increased nitrate level in dialysate of incubation mixture, which contained homogenate/crude extract, protease inhibitors and a PN-treated substrate, such as treated histone (III-S), BSA or invertase. Enhanced activity of nitratases was noted by preincubating crude extract with Ca2+. In addition, at least two types of nitratases may occur: type I, reductant-dependent, and type II, reductant- independent. Furthermore, upon denitration, the activity of PN-treated invertase increased to the same activity level of the untreated invertase. The overall reaction catalyzed by nitratases for denitration of nitrotyrosine residues in protein could be as follows: Protein-Tyr-NO2 + H2O --> Protein-Tyr-H + H+ + NO3-. The nitration/denitration of protein-tyrosine may be crucial in regulating signal transduction.

Modification of proteins and polynucleotides by peroxynitrite

Varied intensities of nitrotyrosine immunoreactivity were detected by Western blots after the reaction of proteins or enzymes with peroxynitrite (PN), a strong oxidant derived from nitric oxide. Intense immunoreactivity of cAMP-dependent protein kinase, calmodulin and most histones may depend on greater access to tyrosine residues in the reaction, whereas the absence of immunoreactivity of caspase-3, ubiquitin and S-100 proteins may reflect lack of accessibility. In addition, the changes in UV/visible absorbency were observed after PN-treatment of polynucleotides, polypeptides or proteins. Brief PN-treatment of invertase increased its enzymatic activity. Furthermore, PN-treatment of rabbit IgG decreased its recognition by anti-IgG. The results suggest that PN may chemically modify polypeptides, proteins and polynucleotides and may subsequently alter their biological activity.

Denitration of peroxynitrite-treated proteins by "protein nitratases" from dog prostate

Putative "protein nitratases," which catalyze denitration of peroxynitrite (PN)-treated, proteins, were detected in the crude extract of dog prostate. Nitratase activity was monitored by the decreased intensity of nitrotyrosine immunoreactive-bands in Western blot and increased nitrate level in dialysate of incubation mixture, which contained prostate crude extract, protease inhibitors and a PN-treated substrate, such as treated histone (III-S), BSA, invertase, or polylysine. Nitratases were activated by preincubation with m-calpain/Ca2+. Furthermore, after denitration, the activity of PN/DTT-treated invertase decreased to the similar activity level of DTT-treated invertase. At least two different types of nitratases may occur: type I, reductant-dependent, and type II, reductant-independent.

Constitutive nitric oxide synthase in Saccharomyces cerevisiae

After removing nonspecific immunoreactivities from crude extract by immunoaffinity chromatography, an immunoreactive-band at 60 kDa of constitutive nitric oxide synthase (cNOS) from Saccharomyces cerevisiae was detected by Western blot using mouse monoclonal anti-neuronal NOS (cNOS). The activity of yeast cNOS, which was prepared by either histone-agarose chromatography or anti-neuronal NOS immunoprecipitation, was monitored by the formation of citrulline. Yeast cNOS was activated in the presence of calmodulin and arginine, whereas it was inhibited by L-NAME, a mammalian NOS inhibitor. Moreover, actinomycin-D decreased the extracellular and the intracellular levels of nitrate and nitrite which had been converted from NO. The results suggest that cNOS occurs in unicellular eukaryotes and the enzyme activity can be regulated.

Soluble guanylate cyclase in Saccharomyces cerevisiae

After removing nonspecific immunoreactivities from crude extract by immunoaffinity chromatography, an immunoreactive-band at 40kDa of soluble guanylate cyclase (SGC) from Saccharomyces cerevisiae was detected by Western blot using rabbit anti-beta 1 subunit of SGC. Cyclic GMP level and SGC activity was measured by ELISA. Immunoprecipitated yeast SGC was activated by sodium nitroprusside, whereas inhibited by 1H-(1,2,4)oxadiazolo(4,3-A)quinoxalin-1-one. Increased cyclic GMP level was also noted when intact yeast cells were incubated with s-nitrosoglutathione, a NO donor. The result implies that NO can be utilized intracellularly and extracellularly. Moreover, the presence of SGC suggests the significance of NO/cyclic GMP signaling in unicellular eukaryotes.

The presence/absence of Bcl-2, Ca2+/calmodulin-dependent protein kinase IV, calretinin and p53 in baker's yeast and wheat germ

After removing the nonspecific immunoreactivities from crude extracts of Saccharomyces cerevisiae and wheat germ by immunoaffinity chromatography, the presence of Ca(2+)-related proteins was tested by Western blot analysis. Immunoreactivity for Bcl-2 was absent in the yeast, whereas the immunoreactivity was evident in wheat germ and remained unchanged after incubation for 4 h with or without actinomycin D. Such incubation caused the degradation of immunoreactive-peptides of Ca2+/calmodulin-dependent protein kinase IV (CaMPK IV) in the yeast and wheat germ. Calretinin and p53 were absent in the yeast and wheat germ. The level of cyclic AMP in the yeast increased 100% after incubation for 30 min with actinomycin D. These results suggest that actinomycin D may not affect intracellular levels of these calcium-related proteins in the yeast and wheat germ, and that Bcl-2 occurs in multicellular eukaryotes. Moreover, the cellular level of CaMPK IV may vary during the onset of cell division and differentiation.

Immunoreactivities of p11 and calcyclin in baker's yeast, wheat germ and lobster

After effectively eliminating the nonspecific cross-immunoreactivity with the affinity columns of anti-IgG agarose and IgG agarose, the potent immunoreactivities of p11 and calcyclin in wheat germ, lobster tail muscle, and three strains of baker's yeast were analyzed by Western blotting using mouse anti-p11 and rabbit anti-calcyclin. The occurrence of multiple bands may be due to either autolyses and/or the interactions between the p11 (or calcyclin) and other endogenous biological molecules. The results suggest not only a ubiquitous distribution and a universal Ca(2+)-mediating regulatory role of p11 and calcyclin in eukaryotes, but also an evolutionary conservation of these (S-100)-related proteins.

Interaction of polyadenylic acid (5') with histone H1 or protamine

The interaction between polyadenylic acid (5') (poly [A]) and histone (or protamine) was analyzed by electrophoretic retardation of poly [A]-histone (or protamine) complex in agarose gel. The potency of interaction was protamine > histone H1, arginine-rich histone > other histones. The catalytic subunit of cyclic AMP-dependent protein kinase effectively decreased the electrophoretic retardation of poly [A]-histone H1. The interaction between poly [A] and histone H1 was also detected by the drastically enhanced absorbance around 340 nm. The findings may implicate a regulatory role of histone H1 on mRNAs through its binding on poly [A] tails.

Immunoreactivities of m-calpain, calpastatin, nitric oxide synthase, myelin basic protein and dynamin II in baker's yeast, wheat germ and lobster tail muscle

Vertebrate m-calpain, calpastatin, constitutive nitric oxide synthase, myelin basic protein, and dynamin I are substrates of protein kinase C (PKC). The presence/absence of similar/related protein in nonvertebrate was investigated by immunological methods, including (1) affinity chromatography on agarose-secondary antibodies and agarose IgG for removal of nonspecific immunoreactivities from crude extracts; (2) omitting beta-mercaptoethanol treatment and boiling prior to SDS-PAGE to increase the immunoreactivity; (3) immunoreactivity comparisons of nonspecific IgG as controls with specific anti-(vertebrate PKC-substrates/related proteins) in Western blots. It was found that (a) m-calpain and dynamin I were absent in baker's yeast, wheat germ and lobster tail muscle, (b) m-calpain, nitric oxide synthase, myelin basic protein and dynamin II were present in all three samples, and (c) calpastatin was present in baker's yeast and lobster tail muscle. The presence and absence of these proteins suggest evolutionary conservation and divergence, respectively, of these PKC substrates.

Immunoreactivities of PKC delta, eta, zeta in baker's yeast, lobster and wheat germ

Varied immunoreactive bands of protein kinase C delta (PKC delta), PKC eta, and PKC zeta were detected in crude extracts of wheat germ, lobster tail meat, and three strains of baker's yeast by analysis of Western blots. Protease-deficient and Fleischmann's Active Dry yeasts exhibited immunoreactivity of PKC delta, whereas wheat germ and Fleischmann's RapidRise yeast displayed immunoreactivities of both PKC delta and PKC zeta. Lobster tail meat showed immunoreactivities of PKC eta and PKC zeta. These positive and negative immunoreactivities reflected evolutionary conservation and divergence, respectively, of these PKC isozymes in eukaryotes.

Immunoreactivity of PKC gammalambda and RACK1 in baker's yeast, lobster and wheat germ

Varied patterns of immunoreactive bands of protein kinase C gamma (PKC gamma) and receptor for activated C-kinase-1 (RACK1) were detected by analysis of Western blots in crude extracts of wheat germ, lobster tail meat, and three strains of baker's yeast. Anti-PKC lambda also reacted with wheat germ and yeast extracts, but failed to react with the lobster extract. The findings may implicate a regulatory role and an evolutionary conservation of these PKC isoenzymes and their receptor proteins in eukaryotes.

Calpain immunoreactivity in baker's yeast, lobster and wheat germ

The immunoreactivities of mu-calpain and m-calpain in wheat germ, lobster tail meat, and three strains of yeast were analysed by Western blotting using mouse anti-mu-calpain and rabbit anti-m-calpain. The occurrence of multiple bands may be due to either autolyses or the interactions between the calpains and other molecules. The results suggest not only a ubiquitous distribution and a universal regulatory role of calpain in eukaryotes, but also an evolutional conservation of calpain.

Immunoreactivity of S-100 protein in baker's yeast, lobster, and wheat germ

The immunoreactivity of S-100 proteins in three strains of yeast and wheat germ was observed by analysis of Western blotting with rabbit anti-bovine S-100. A high level of activity was exhibited in wheat germ, whereas a very low level was found in lobster tail meat. The occurrence of multiple bands may be due to the interactions between S-100A and S-100B and/or other molecules. The highly evolutionally conserved S-100 may play an important role in cellular signal transduction and cell growth in yeast and wheat germ.

Phosphorylation of endogenous substrates of yeast protein kinase C regulated by lipid-triton micelles

In the DE-52 fraction 19 of the crude cytosolic extract of Saccharomyces cerevisiae, the 31-kDa endogenous substrate(s) of protein kinase C were detected by SDS-polyacrylamide gel electrophoresis and autoradiography. Phosphorylation of the substrate(s) depended on Ca2+, phosphatidylserine and diacylglycerol. It was also enhanced by phosphatidylinositol, phosphatidylethanolamine and phosphatidylglycerol (dioleoyl), but inhibited by arachidonic acid and sphingosine.

Regulation of the phosphorylation of calpain II and its inhibitor

Phosphorylation of calpain II (or its inhibitor) by the catalytic subunit of cyclic AMP-dependent protein kinase (A-PK), cyclic GMP-dependent protein kinase (G-PK), and protein kinase C (PK-C) was analyzed by SDS-polyacrylamide gel electrophoresis and autoradiography. Among these protein kinases, the catalytic subunit of A-PK exhibited the strongest phosphorylations of both calpain II and its inhibitor. Arachidonic acid and staurosporine effectively inhibited phosphorylation regardless the type of kinase tested. Despite its lack of effect on the phosphorylation of calpain II by the catalytic subunit of A-PK, sphingosine moderately enhanced the phosphorylation of calpain II by G-PK. Other agents, including phosphatidylethanolamine, phosphatidylinositol and 1, 2-dioleoyl-sn-glycerol, had no significant effect.

Enhanced phosphorylation of yeast endogenous substrates by phosphatidylglycerol (dioleoyl) and phosphatidylinositol

Protein kinases and their endogenous substrates from the crude cytosolic extract of Saccharomyces cerevisiae were coeluted in the fraction 13 on DE-52 column chromatography. Analyses of SDS-polyacrylamide gel electrophoresis and autoradiography revealed that the peptides between 14 and 34 kDa were the major phosphorylated substrates. In the presence of Ca2+ and Mg2+, the phosphorylation was suppressed strongly by the regulatory subunit of cAMP-dependent protein kinase and slightly by oleic acid, whereas it was augmented appreciably by phosphatidylglycerol (dioleoyl) and phosphatidylinositol.

Regulation of fungal proteolysis on cyclic AMP-dependent protein kinase, cyclic AMP phosphodiesterase, glycogen synthase and histones

Limited proteolysis of catalytic and regulatory subunits of cyclic AMP-dependent protein kinase (A-pk), cyclic AMP phosphodiesterase, glycogen synthase, and histones by fungal protease (type XIX) was analyzed by the digested peptide bands in SDS polyacrylamide gel electrophoresis. The modulatory effects on proteolysis by nucleotides, polypeptides, and phospholipids may greatly depend on the intrinsic nature of substrates. The proteolysis of the regulatory subunit of A-pk and glycogen synthase was not regulated by nucleotides and nucleic acids. In comparison, phosphatidyl serine, cardiolipin, and pepstatin A stimulated the proteolysis of the catalytic subunit of A-pk. Whereas, lambda DNA (Hind III digest), t-RNA, GTP-, phosphatidyl serine, sphingosine inhibited the proteolysis of cyclic AMP phosphodiesterase. Moreover, MS2 RNA, lambda DNA, t-RNA, dGTP, Phosphatidyl serine, phosphatidyl inositol, antipain, and chymostatin exerted inhibitory proteolytic effect on histone VIII-S. Some of these agents also had similar inhibitory effect on other types of histones (types III-S and VII-S). The inhibitory effect of phosphatidyl serine on proteolysis of histone may be due to their interaction which was monitored by the drastic increase of uv absorbance.

Stimulation of proteolysis on calmodulin

The proteolysis of calmodulin by fungal protease (type XIX) was greatly enhanced in the presence of dGTP and MS2 RNA. Whereas, only moderate proteolytic activation on bacterial proteases (type XXVI) was observed in the presence of MS2 RNA. No appreciable proteolysis of calmodulin by bacterial protease (type IX) was observed. Proteolytic fragments of calmodulin cleaved by fungal protease exhibited unusual low mobility during SDS-polyacrylamide gel electrophoresis. Similar decreased electrophoretic mobility was also noted in the proteolytic fragments of other Ca2(+)-binding proteins including S-100A protein and parvalbumin.

Regulatory effects of S-100 protein and parvalbumin on protein kinases and phosphoprotein phosphatases from brain and skeletal muscle

In the eluted fractions of histone-treated crude extracts separated by Sephadex G-200 filtration, multiple protein kinase (PK) activities, including three from brain and two from skeletal muscle, were augmented by both S-100 protein and parvalbumin on the phosphorylation of endogenous substrates. One additional PK activity suppressed by both S-100 and parvalbumin was also found in muscle. In comparison, phosphoprotein phosphatases (PPase), which were also prepared by the same procedure of initial step of histone-treatment followed by the steps of Bio-Gel P-6DG for brain and DNA-cellulose for muscle, were all activated by S-100 while inhibited by parvalbumin and phosphatidylserine.

Multiforms of megamodulin-dependent protein kinases from baker's yeast

Multiforms of megamodulin-dependent protein kinases (M-PK) were partially purified from baker's yeast by excluding endogenous megamodulin with histone, and then by gel filtration with Sephadex G-200. The stimulation of M-PK in the presence of Mg2+, Mn2+ or Co2+ was enhanced by yeast megamodulin. In addition, similar augmented activity of M-PK was also noted in the presence of Mg2+ by megamodulins prepared from E. coli, bovine brain and wheat germ.

Stimulation of mammalian and yeast phosphoprotein phosphatases by megamodulins from various sources

Phosphoprotein phosphatases (PPase) were isolated from either the rabbit cerebral cortex or Baker's yeast by excluding endogenous megamodulin with histone, and then by desalting cations with Bio-Gel P-6DG filtration. The stimulation of PPase in the presence of Mn2+ was greatly enhanced by megamodulins prepared from various sources including rabbit brain, Baker's yeast, wheat germ, and Escherichia coli (E. coli). Moreover, the augmented activity of PPase was also demonstrated in the presence of [megamodulin-Mn2+] complex.

Interactions between basic proteins and stimulatory protein kinase modulator

The interactions of a number of basic proteins with stimulatory protein kinase modulator (PKMs) from the mouse brain were measured by absorbance at 360 nm. Such interactions were not altered in the presence of Mg2+ at low concentrations.

Tissue energy of mammalian modulator-dependent protein kinases

The levels of modulator-dependent protein kinases and protamine-dependent protein kinase(s) in various tissues of adult mice were compared. Cerebellum contained the highest levels of both modulator-dependent protein kinases and protamine-dependent protein kinase(s), whereas skeletal muscle contained no detectable enzymes. The lung and the ileum were also rich in modulator-dependent protein kinases, while other tissues were poor sources of these enzymes.

Separation between modulator-dependent protein kinases I and II

The separation of modulator-dependent protein kinase I from modulator-dependent protein kinase II obtained from the lungs of sexually premature male mice was accomplished by Sephadex G-200 gel filtration. After preincubation of a mouse lung cytosol fraction with arginine-rich histone, theophylline, cyclic GMP and crude protein kinase modulator a cyclic GMP-dependent protein kinase activity peak present in a non-preincubated sample completely disappeared and was replaced by a late-eluted modulator-dependent protein kinase II peak. There was a difference in substrate specificity between modulator-dependent protein kinase I and modulator-dependent protein kinase II despite their similar dependence on crude protein kinase modulator or partially purified stimulatory protein kinase modulator for their maximal activities.

Conversion of mammalian cyclic GMP-dependent protein kinase into modulator-dependent protein kinase (type II) in vitro

The spontaneous conversion of mammalian cyclic GMP-dependent protein kinase (G-PK) into modulator-dependent protein kinase (type II) (M-PKII) in the absence of cGMP or histone was observed in vitro. The findings, together with similarity in substrate protein specificity, suggest that M-PKII is the catalytic subunit of mammalian G-PK.

Separation of modulator-dependent protein kinase (type I) from cyclic GMP-dependent protein kinase in mouse testes

A new type of enzyme, modulator-dependent protein kinase (type I) (M-PKI), was successfully isolated from the cytosol fraction of mouse testes. It was eluted slightly after the peak of cyclic GMP-dependent protein kinase (G-PK) by Sephadex G-200 gel filtration. Unlike either cyclic AMP-dependent protein Kinase (A-PK) or G-PK, its maximal activity depended exclusively on the presence of crude protein kinase modulators (PKM) or partially purified stimulatory modulator (PKMs).

Changes in the activities of protein kinase modulators in the cerebellum of mice due to ethanol, caffeine, or phenobarbital administration

Decreased activities of both the inhibitory modulator of adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase (A-PK) as well as the stimulatory modulator of guanosine 3':5'-monophosphate (cGMP)-dependent protein kinase (G-PK) from the mouse cerebellum were noted due to the administration of excessive doses of ethanol, caffeine, and phenobarbital for up to 28 days. The dose-dependent of the inhibition of A-PK or the stimulation of G-PK was observed as a function of the amount of protein kinase modulators in the cerebellum of mice receiving different doses of ethanol.

Ontogenetic changes in relative levels of cyclic AMP-dependent and cyclic GMP-dependent protein kinases in prostates, epididymides and testes from guinea-pigs

Changes in relative levels of cyclic AMP-dependent protein kinase (A-PK) and cyclic GMP-dependent protein kinase (G-PK) in prostates, epidymides and testes from guinea-pigs were examined at 3 different ages. During postnatal development, a decrease in the ratio of the 2 classes of protein kinases was seen in prostates, whereas increases of the ratios of the enzymes were found in epididymides and testes.

Cyclic GMP-dependent and cyclic AMP-dependent protein kinases, protein kinase modulators and phosphodiesterases in arteries and veins of dogs. Distribution and effects of arteriovenous fistula and arterial occlusion

Possible involvement of cyclic GMP-dependent and cyclic AMP-dependent protein kinases, protein kinase modulators and cyclic nucleotide phosphodiesterases in functions of vascular tissues were investigated in the dog. All of the above activities, localized in the smooth muscle-rich inner layer of the blood vessels, were found to be higher in the arteries than in the veins. The peripheral arteries were disproportionately richer in cyclic GMP-dependent protein kinase (as indicated by high ratios of cyclic GMP-dependent to cyclic AMP-dependent protein kinase) than were the veins, with the exception of the pulmonary artery, an atypical arterial tissue exposed to low blood pressure. Interestingly, the protein kinase ratio for the aorta, an artery with no significant role in blood pressure regulation, was not higher than that for the vena cava. Creation of femoral arteriovenous fistulae in the dogs led to preferential reductions in the cyclic GMP-dependent enzyme activity both in the proximal and distal arteries, whereas it was elevated in the stressed vein distal to the anastomotic site. The cyclic GMP-dependent enzyme was preferentially reduced in the saphenous artery distal to occlusion. Changes in the cyclic GMP-dependent enzyme activity appeared to precede gross atrophy or hypertrophy of the vessels. It is suggested that the vascular cyclic GMP-dependent protein kinase may be closely related to peripheral resistance and its regulation.

Isolation of stimulatory modulator of guanosine 3':5'-monophosphate-dependent protein kinase from mammalian heart devoid of inhibitory modulator of adenosine 3':5'-monophosphate-dependent protein kinase

The stimulatory and inhibitory activities in the crude preparation of protein kinase modulator from dog heart were separated by Sephadex G-100 gel filtration, and the stimulatory modulator was further purified by DEAE-cellulose chromatography. The isolated stimulatory modulator, as the crude modulator preparation, stimulated the activity of the purified guanosine 3':5'-monophosphate (cGMP)-dependent protein kinases of both mammalian and arthropod origins in the presence of cGMP. The cGMP-dependent protein kinases were not activated by cGMP in the absence of either the isolated stimulatory modulator or the crude modulator. The stimulatory modulator, unlike the crude modulator had no effect on the activity of adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase. The stimulatory modulator was a protein since its activity was destroyed by trypsin but was resistant to hydrolysis by DNase, RNase, phospholipase C, and lysozyme. The isolated inhibitory modulator, presumably the same as the protein inhibitor of cAMP-dependent protein kinase reported by Walsh et al. (Wash. D.A., Ashby, C.D., Gonzalez, C., Calkins, D., Fischer. E.H., and Krebs, E.G. (1971) J. Biol. Chem. 246, 1977-1985), depressed the cAMP-stimulated activity of cAMP-dependent protein kinase as did the crude preparation of protein kinase modulator. The isolated inhibitory modulator, unlike the crude preparation, was without effect on cGMP-dependent protein kinase. The present findings provide evidence to support that in mammals there are separate proteins for the stimulatory and the inhibitory activities of protein kinase modulator, in contrast to the modulator from an arthropod tissue (lobster tail muscle, Donnelly et al. (Donnelly, T.E., Jr., Kuo, J.F., Reyes, P.L., Liu, Y.P., and Greengard, P. (1973) J. Biol. Chem. 248, 190-198) which has been shown to possess both activities.

Stimulatory modulator of guanosine 3':5'-monophosphate-dependent protein kinase from mammalian tissues

The crude protein kinase modulator preparations obtained from several rat tissues (aorta, brain heart, liver, lung, skeletal muscle, small intestine and testis) were separated into their stimulatory and inhibitory modulator components by Sephadex G-100 gel filtration. The isolated stimulatory modulator augmented the activity of guanosine 3':5'-monophosphate-dependent protein kinase. The isolated inhibitory modulator, on the other hand, depressed the activity of cyclic AMP-dependent protein kinase; it was without effect on the activity of cyclic GMP-dependent protein kinease. The present findings indicate that in the mammal, apparently in contrast to the arthropoda, separate proteins are responsibile for the stimulatory and the inhibitory activities of protein kinase modulator and that the two classes of cyclic nucleotide-dependent protein kinase are regulated in an opposing manner by these two types of modulators.

Purification and general properties of guanosine 3':5'-monophosphate-dependent protein kinase from guinea pig fetal lung

Guanosine 3':5'-monophosphate (cyclic GMP)-dependent protein kinase was purified from the guinea pig fetal lung, a tissue shown to be the richest in this enzyme in all mammalian sources examined, and its general properties studied. The enzyme was purified 150-fold from crude extract by steps of pH 5.4 isoelectric precipitation, Sephadex G-200 filtration, hydroxylapatite treatment and DEAE-cellulose chromatography. The purified enzyme, free from contamination with adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase, had a specific activity at least equivalent to 600-fold purification of the enzyme from the adult lung. The pulmonary enzyme exhibited an absolute requirement of protein kinase modulator (prepared from various mammalian tissues with an exception of skeletal muscle) for its activity. Inhibitor protein of cyclic AMP-dependent protein kinase purified from rabbit skeletal muscle could not stimulate nor inhibit the cyclic GMP target enzyme, indicating the factors from mammalian sources regulating the two classes of protein kinases may not be the same. The enzyme had Ka values of 1.3 times 10(-8) and 3.3 times 10(-8) M for 8-bromo cyclic GMP and cyclic GMP, respectively, compared to 3.0 times 10(-6) M for cyclic AMP. Cyclic GMP lowered the Km of the enzyme for ATP from 6.3 times 10(-5) M in its absence to 2.1 times 10(-5) M in its presence, accompanied by an approximate doubling of the Vmax. The molecular weight of the enzyme (assayed by its catalytic and cyclic GMP-binding abilities) was estimated to be 123,000, corresponding to a sedimendation coefficient of 7.06 S, by means of sucrose density gradient ultracentrifugation. The cyclic GMP-dependent enzyme required Mg2+ and Co2+ for its activity with optimal concentrations of about 30 and 0.7 mM, respectively. The maximal activity seen in the presence of Mg2+, however, was nearly twice as high as that seen in the presence of Co2+. Histones were generally effective substrates for the enzyme, whereas protamine, casein, phosvitin, phosphorylase kinase, and activator protein of phosphodiesterase were not. The cyclic GMP-dependent enzyme exhibited a greater affinity for histones than did the cyclic AMP-dependent enzyme in the presence of Mg2+.