Protein kinase activities in cell-free extracts of Streptomyces coelicolor A3(2)

Low-temperature synthesis of hierarchical structures of copper oxide and their superior biological activity

In this work, the authors report a facile low-temperature wet-chemical route to prepare morphology-tailored hierarchical structures (HS) of copper oxide. The preparation of copper oxide collides was carried out using varying concentrations of copper acetate and a reducing agent at a constant temperature of 50°C. The prepared HS of CuO were characterised by powdered X-rays diffraction that indicates phase pure having monoclinic structures. The morphology was further confirmed by field-emission scanning electron microscope. It reveals a difference in shape and size of copper oxide HS by changing the concentration of reactants. In order to evaluate the effect of H2O2 on CuO NPs, the prepared CuO are modified by treatment with H2O2. In general trend, CuOH2O2 collide showed enhanced protein kinase inhibition, antibacterial (maximum zone 16.34 mm against Staphylococcus aureus) and antifungal activities in comparison to unmodified CuO collides. These results reveal that CuO HS exhibit antimicrobial properties and can be used as a potential candidate in pharmaceutical industries.

Green synthesised zinc oxide nanostructures through Periploca aphylla extract shows tremendous antibacterial potential against multidrug resistant pathogens

To grapple with multidrug resistant bacterial infections, implementations of antibacterial nanomedicines have gained prime attention of the researchers across the globe. Nowadays, zinc oxide (ZnO) at nano-scale has emerged as a promising antibacterial therapeutic agent. Keeping this in view, ZnO nanostructures (ZnO-NS) have been synthesised through reduction by P. aphylla aqueous extract without the utilisation of any acid or base. Structural examinations via scanning electron microscopy (SEM) and X-ray diffraction have revealed pure phase morphology with highly homogenised average particle size of 18 nm. SEM findings were further supplemented by transmission electron microscopy examinations. The characteristic Zn-O peak has been observed around 363 nm using ultra-violet-visible spectroscopy. Fourier-transform infrared spectroscopy examination has also confirmed the formation of ZnO-NS through detection of Zn-O bond vibration frequencies. To check the superior antibacterial activity of ZnO-NS, the authors' team has performed disc diffusion assay and colony forming unit testing against multidrug resistant E. coli, S. marcescens and E. cloacae. Furthermore, protein kinase inhibition assay and cytotoxicity examinations have revealed that green fabricated ZnO-NS are non-hazardous, economical, environmental friendly and possess tremendous potential to treat lethal infections caused by multidrug resistant pathogens.

Protein tyrosine phosphorylation in streptomycetes

Using phosphotyrosine-specific antibodies, we demonstrate that in several Streptomyces spp. a variety of proteins are phosphorylated on tyrosine residues. Tyrosine phosphorylation was found in a number of Streptomyces species including Streptomyces lividans, Streptomyces hygroscopicus and Streptomyces lavendulae. Each species exhibited a unique pattern of protein tyrosine phosphorylation. Moreover, the patterns of tyrosine phosphorylation varied during the growth phase and were also influenced by culture conditions. We suggest that metabolic shifts during the complex growth cycle of these filamentous bacteria, and possibly secondary metabolic pathways, may be controlled by the action of protein tyrosine kinases and phosphatases, as has been demonstrated in signal transduction pathways in eukaryotic organisms.

Inhibition of sporulation, glycopeptide antibiotic production and resistance in Streptomyces toyocaensis NRRL 15009 by protein kinase inhibitors

Production of the glycopeptide antibiotic A47934 by Streptomyces toyocaensis NRRL 15009 begins in the late exponential phase in liquid culture and peaks in the early stationary phase. The pattern of cellular phosphoprotein production changes upon onset of A48934 production with the appearance of several novel phosphoproteins only when an antibiotic is being produced. Phosphoamino acid analysis revealed that S. toyocaensis NRRL 15009 produces proteins phosphorylated on His, Ser, Thr and Tyr, with most being membrane-associated. Addition of the isoflavones genistein or quercetin abolishes A47934 production in liquid culture and sporulation on solid medium. Furthermore, genistein slows the onset of inducible glycopeptide antibiotic resistance in S. toyocaensis NRRL 15009. These results support the participation of protein kinase pathways in A47934 biosynthesis and resistance and cell differentiation in S. toyocaensis NRRL 15009.

Evidence for phosphoprotein phosphatase in Streptomyces granaticolor

The existence of phosphoprotein phosphatase (PPP) in aerial mycelium of S. granaticolor was demonstrated. Using inhibitors of serine and/or threonine PPP and specifically labeled substrate it was found that the PPP is of the serine and/or threonine type.

Aminoglycoside antibiotic phosphotransferases are also serine protein kinases

BACKGROUND

Bacterial resistance to aminoglycoside antibiotics occurs primarily through the expression of modifying enzymes that covalently alter the drugs by O-phosphorylation, O-adenylation or N-acetylation. Aminoglycoside phosphotransferases (APHs) catalyze the ATP-dependent phosphorylation of these antibiotics. Two particular enzymes in this class, APH(3')-IIIa and AAC(6')-APH(2"), are produced in gram-positive cocci and have been shown to phosphorylate aminoglycosides on their 3' and 2" hydroxyl groups, respectively. The three-dimensional structure of APH (3')-IIIa is strikingly similar to those of eukaryotic protein kinases (EPKs), and the observation, reported previously, that APH(3')-IIIa and AAC(6')-APH(2") are effectively inhibited by EPK inhibitors suggested the possibility that these aminoglycoside kinases might phosphorylate EPK substrates.

RESULTS

Our data demonstrate unequivocally that APHs can phosphorylate several EPK substrates and that this phosphorylation occurs exclusively on serine residues. Phosphorylation of Ser/Thr protein kinase substrates by APHs was considerably slower than phosphorylation of aminoglycosides under identical assay conditions, which is consistent with the primary biological roles of the enzymes.

CONCLUSIONS

These results demonstrate a functional relationship between aminoglycoside and protein kinases, expanding on our previous observations of similarities in protein structure, enzyme mechanism and sensitivity to inhibitors, and suggest an evolutionary link between APHs and EPKs.

Constitution of the metabolic type of streptomycetes during the first hours of cultivation

Using the examples of biosynthesis of streptomycin, bialaphos, actinorhodin, oligoketides and autoregulators during the first hours of streptomycete cultivation, it is stressed that the external environment in cooperation with the internal metabolic abilities of the cell determines the metabolic type that would develop during the life cycle of the producing streptomycetes. If we accept that a certain metabolic type (from the point of view of the production of secondary metabolites) was determined already during the first hours of cultivation of the microorganisms, we must also admit that the availability of primary metabolites in the so-called production phase of growth (stationary phase, idiophase, etc.) is to a certain extent determined by the very early stages of strain development.

Proteins that interact with GTP in Streptomyces griseus and its possible implication in morphogenesis

By cross-linking with [alpha-32P]GTP or [gamma-32P]GTP with or without UV treatment, several proteins of Streptomyces griseus were shown to interact with GTP in specific ways. After gel electrophoresis, 19 bands of radioactivity were found; 12 bands were assigned as GTP-binding proteins and 6 bands as phosphorylated proteins. One band was assumed to be a guanylylated protein. The profile of radioactive bands was similar between cells prepared from liquid or solid culture, but markedly different between growth phases. A mutant (strain M-1) defective in aerial mycelium formation, which was originally found as a decoyinine-resistant isolate, was found to have a different profile of phosphorylated proteins.

Cloning, purification, and properties of a phosphotyrosine protein phosphatase from Streptomyces coelicolor A3(2)

We describe the isolation and characterization of a gene (ptpA) from Streptomyces coelicolor A3(2) that codes for a protein with a deduced M(r) of 17,690 containing significant amino acid sequence identity with mammalian and prokaryotic small, acidic phosphotyrosine protein phosphatases (PTPases). After expression of S. coelicolor ptpA in Escherichia coli with a pT7-7-based vector system, PtpA was purified to homogeneity as a fusion protein containing five extra amino acids. The purified fusion enzyme catalyzed the removal of phosphate from p-nitrophenylphosphate (PNPP), phosphotyrosine (PY), and a commercial phosphopeptide containing a single phosphotyrosine residue but did not cleave phosphoserine or phosphothreonine. The pH optima for PNPP and PY hydrolysis by PtpA were 6.0 and 6.5, respectively. The Km values for hydrolysis of PNPP and PY by PtpA were 0.75 mM (pH 6.0, 37 degrees C) and 2.7 mM (pH 6.5, 37 degrees C), respectively. Hydrolysis of PNPP by S. coelicolor PtpA were 0.75 mM (pH 6.0, 37 degrees C) and 2.7 mM (pH 6.5, 37 degrees C), respectively. Hydrolysis of PNPP by S. coelicolor PtpA was competitively inhibited by dephostatin with a Ki of 1.64 microM; the known PTPase inhibitors phenylarsine oxide, sodium vanadate, and iodoacetate also inhibited enzyme activity. Apparent homologs of ptpA were detected in other streptomycetes by Southern hybridization; the biological functions of PtpA and its putative homologs in streptomycetes are not yet known.

Rapid inhibition of protein histidine phosphorylation by UV-irradiation in Xanthomonas oryzae pv. oryzae

Exposure of Xanthomonas oryzae pv. oryzae cells to 254 nm UV radiation resulted in an alteration of protein phosphorylation. Labelling of the phosphohistidine-containing proteins with molecular masses of 81 and 32 kDa, named p81 and p32, was rapidly reduced following UV irradiation in the early exponential cells, but the decrease was not detected in mid-exponential cells. Mitomycin C, a DNA replication inhibitor, and rifampicin, a drug generally used to inhibit RNA synthesis and DNA replication, were also found to reduce the histidyl phosphorylation. However, this alteration of protein phosphorylation was not hindered by chloramphenicol treatment. A possible role for these histidyl phosphoproteins in sensing UV light is proposed.

Metabolism of phosphate-limited cultures of Streptomyces. IV. Protein-phosphorylation of antibiotics-producing cultures

It has been demonstrated that in the cellular proteins of Streptomyces hygroscopicus JA 6599 and Streptomyces noursei JA 3890 b, the producers of the antibiotics turimycin and nourseothricin, respectively, phosphorylated proteins are present. Numbers and concentrations of phosphorylated proteins decreased during the idiophase as characterized by phosphate limitation, antibiotic biosynthesis and phosphatase formation. Phosphoamino acids of serine, threonine and tyrosine were found in the hydrolysates of proteins. Protein tyrosyl kinase was demonstrated in the cellular extracts. The results supports the hypothesis that protein phosphorylation possesses a function in the regulation of growth and secondary product formation.

Effects of protein kinase inhibitors on in vitro protein phosphorylation and cellular differentiation of Streptomyces griseus

In vitro phosphorylation reactions using extracts of Streptomyces griseus cells and gamma-[32P]ATP revealed the presence of multiple phosphorylated proteins. Most of the phosphorylations were distinctly inhibited by staurosporine and K-252a which are known to be eukaryotic protein kinase inhibitors. The in vitro experiments also showed that phosphorylation was greatly enhanced by manganese and inhibition of phosphorylation by staurosporine and K-252a was partially circumvented by 10 mM manganese. A calcium-activated protein kinase(s) was little affected by these inhibitors. Herbimycin and radicicol, known to be tyrosine kinase inhibitors, completely inhibited the phosphorylation of one protein. Consistent with their in vitro effects the protein kinase inhibitors inhibited aerial mycelium formation and pigment production by S. griseus. All these data suggest that S. griseus possesses several protein kinases of eukaryotic type which are essential for morphogenesis and secondary metabolism. In vitro phosphorylation of some proteins in a staurosporine-producing Streptomyces sp. was also inhibited by staurosporine, K-252a and herbimycin, which suggests the presence of a mechanism for self-protection in this microorganism.

Streptomycin biosynthesis and its regulation in Streptomycetes

New insights into the gene orders, structures, evolution, and functions of streptomycin (Sm) biosynthetic genes (str) were gained via hybridization studies, determination of nucleotide sequences, and measurement of expression in the str gene clusters of Streptomyces griseus and S. glaucescens. Both str clusters showed considerable divergence in macro and micro structure. Genes putatively involved in pathways leading to the (dihydro-)streptose and N-methyl-L-glucosamine moieties of Sm were identified. Additional regulatory elements, such as gene strS and conserved TTA codons in the N-terminal sections of reading frames, are reported. Evidences for the involvement of physiological state, signal transduction, and activators in the control of Sm production are presented.

Protein phosphorylation in response to stress in Clostridium acetobutylicum

The possible involvement of protein phosphorylation in the clostridial stress response was investigated by radioactively labeling growing cells of Clostridium acetobutylicum with 32Pi or cell extracts with [gamma-32P]ATP. Several phosphoproteins were identified; these were not affected by the growth stage of the culture. Although the extent of protein phosphorylation was increased by heat stress, the phosphoproteins did not correspond to known stress proteins seen in one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Purified clostridial DnaK, a stress protein, acted as a kinase catalyzing the phosphorylation of a 50-kilodalton protein. The phosphorylation of this protein was enhanced in extracts prepared from heat-stressed cells. Diadenosine-5',5"'-P1,P4-tetraphosphate had no influence on protein phosphorylation.