Search

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.

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.

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.

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.

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.

Phosphorylation of endogenous yeast substrates in DE-52 fractions were analysed by SDS-polyacrylamide gel electrophoresis and autoradiography. In fractions 29 and 45, phosphatidylinositol inhibited the phosphorylation of multiple peptides with a wide range of molecular mass whereas it enhanced the phosphorylation of peptides smaller than 14 kD. Similar dual modulation of the phosphorylation by arachidonic acid was observed in fraction 37 which also contained potent phosphatidylserine-activating protein kinase C.

The phosphorylation of histones and glycogen synthase by protein kinases was analysed by SDS-polyacrylamide gel electrophoresis and autoradiography. The phosphorylation of histone III-S by the catalytic subunit of cyclic AMP-dependent protein kinase (A-PK) or cGMP-dependent protein kinase (G-PK) was inhibited by archidonic acid, sphingosine and staurosporine. Using the catalytic subunit of A-PK, the phosphorylation of histone VIII-S was inhibited by Ca2+, arachidonic acid and staurosporine; the phosphorylation of histone II-S was inhibited by phosphatidyl ethanolamine, phosphatidyl inositol, arachidonic acid and staurosporine; and the phosphorylation of glycogen synthase was inhibited by arachidonic acid and staurosporine. After being phosphorylated by the catalytic subunit of A-PK, calpain II with 4 microM Ca2+ was less effective in degrading histone III-S, which had been prephosphorylated by PK-C.

The effects of various agents on the cleavage of serum albumin, interferon, immunoglobulin and complement component C1q by the extracellular protease from Staphylococcus aureus were analysed by SDS-polyacrylamide gel electrophoresis. Arachidonic acid moderately stimulated the proteolysis of serum albumin, interferon and complement component. Phosphatidic acid effectively enhanced the proteolysis of serum albumin and IgG, whereas it inhibited the cleavage of IgM. The proteolysis of IgG was appreciably enhanced by sphingosine. In contrast, phosphatidyl choline and phosphatidyl glycerol were shown to have an inhibitory effect on the proteolysis of IgG and IgM. Phosphatidyl serine, phosphatidyl inositol and phosphatidyl ethanolamine also inhibited the proteolysis of IgG. The failure of any of these agents to exert a persistent effect on the cleavage of all substrates, revealed the complexity of the interactions among the agent, the substrate and the protease.

Limited proteolysis by venoms was analysed by the cleaved peptide band(s) in SDS-polyacrylamide gel electrophoresis. The venom from Crotalus atrox degraded interferon, interleukin-2, IgG, IgM, and a crude form of acetyl cholinesterase but had no effect on IgA. Although the venom from Androctonus australis did not exert appreciable proteolysis on any of the immunoglobulins it had potent proteolytic activities against interferon and interleukin-2. The venom from Vespula maculifrons had only a minor proteolytic effect on interferon. The proteolysis by venoms was not effectively inhibited by alpha 1-antitrypsin or a2-macroglobulin. Moreover, no appreciable proteolytic activity was detected in the venoms from Bufo arenarum, Apis mellifera and Heloderma suspectrum.

Various agents were tested for their effects on microbial proteases, which activity was monitored by the analysis of cleaved peptide bands in SDS-polyacrylamide gel electrophoresis. Using casein as a substrate, fungal protease (type XIX) was inhibited by the phenyl methyl sulphonyl fluoride, chymostatin, antipain and leupeptin, while bacterial protease (type XXVI) was inhibited by phosphatidyl glycerol, phosphatidyl inositol and sphingosine. MS2 RNA exerted minor inhibition on the bacterial proteolysis of regulatory subunits of cyclic AMP-dependent protein kinase (A-PK). The cleavage of DNA binding protein by both proteases was inhibited, in the presence of MS2 RNA and lambda DNA. In comparison, phosphatidyl serine slightly stimulated the fungal protease on the cleavage of ribonuclease T1. RNA polymerase is a good substrate of the bacterial protease as indicated by the generation of multiple cleaved peptide fragments, whereas alkaline phosphatase is not susceptible to proteolysis.

Sephadex G-200 gel filtration of DNA cellulose-treated crude extracts of rat skeletal muscle, revealed a broad peak-fraction of tRNA-inhibitory protein kinases (PK) coeluted endogenous substrates. In comparison, the elution profile of baker's yeast exhibited multiple peak-fractions of tRNA-inhibiting PK. Various tRNA all showed inhibition to PK. In the presence of regulatory subunit of cyclic AMP-dependent protein kinase, tRNA did not exert synergetic inhibition on PK. Moreover, the interaction of tRNA with active muscle PK fractions could not be monitored by the increment of absorbance at 340 nm. tRNA had no significant regulatory effect on the phosphorylation of actin and myosin.

The formation of complexes between cations and stimulatory protein kinase modulator (PKMs) were performed by preincubation and gel filtration. The stimulatory effects of Fe3+, Fe2+, Mg2+, and Co2+ complexes on cerebellar modulator-dependent protein kinases (M-PK) were similar to those without preformation of complexes by preincubation and gel filtration. Antagonism by Ca2+ on the stimulatory effect of Mg2+ was noted in spite of the ineffectiveness of Ca2+ when present alone.

The activity of the catalytic subunit of cyclic AMP-dependent protein kinase (A-PK), utilizing type II-S, III-S histone or protamine (free base) as a substrate, was augmented in the presence of regulatory protein including calmodulin, S-100 protein, parvalbumin, or troponin. However, inhibition by calmodulin or S-100 but stimulation by parvalbumin or troponin on this A-PK subunit was observed when II-S histone was replaced by V-S, VI-S, VII-S, or VIII-S histone. In addition, the stimulatory effect of calmodulin or S-100 on this A-PK subunit utilizing III-S histone was greatly diminished when half the dose of III-S was replaced by other histones in a bi-mixed form.

Basic protein factor I (BPFI was purified to homogeneity from bovine brain by boiling and trichloroacetic acid-precipitation of tissue homogenate, followed by DEAE-cellulose, Sephadex G-150, Affi-Gel-phenothiazine, and Bio-Gel P-6DG chromatographic procedures. The preparation appeared as a single protein band in the SDS-polyacrylamide gel electrophoresis with a minimal Mr of 13,200. The factor was a basic protein as indicated by an estimated isoelectric point of pH 8.3 and a high content of amino acids including arginine, histidine, lysine and others. In the absence of Mn2+, the factor stimulated the phosphoprotein phosphatases (PPase) from rabbit brains. Unlike histones or protamine, the factor was a poor substrate for megamodulin-dependent protein kinase. In addition, the factor did not interact significantly with E. coli megamodulin.

Binding (or interaction) of cortisol with microbial molecule(s) was observed by employing Bio-Gel HTP affinity chromatography and subsequently by fluorescence spectrophotometry. Molecule(s) in the crude extract of baker's yeast and in other microbial proteases exhibited varied degrees of cortisol-binding. Bacterial protease (type IX) had highest, while the type XXVI enzyme had the lowest, binding capacity. In addition, these two proteases exhibited a distinct difference in the alterations of ultraviolet spectra due to interaction with cortisol. Using casein as a substrate, cortisol, CTP, trypsin inhibitor or leupeptin appreciably inhibited type IX protease at low concentrations of Ca2+. However, thyroxine had no effect on this protease.

In the presence of Mg2+ (or Mn2+), the interactions (or bindings) of brain megamodulin with nicotinamide adenine dinucleotide (NAD+/NADH), phosphohistones and adenine triphosphate (ATP) were greatly enhanced. Furthermore, the activity of brain phosphoprotein phosphatases ( PPase ) was augmented by brain [ megamodulin -Mn2+] complex.