Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glucokinase from baker's yeast has been purified to homogeneity. The molecular weight of the subunit is 51,000. The native enzyme sediments with S20,w values in the range of 19 to nearly 4S. The presence of glucose and phosphate favors the heavier species while ATP causes depolymerization. Titration experiments with the Ellman reagent support this view. The enzyme subunit has four sulfhydryl residues of which one is more reactive than the other three. However, it does not seem to be directly responsible for the catalytic activity. The amino acid composition of the enzyme is similar to those of the hexokinases P1 and P2 but for aspartic acid and histidine.
Mol Cell Biochem 1977 Nov 25
PMID:Molecular properties of yeast glucokinase. 34 Sep 36

Some model substrates of the peptidyl transferase centre of E. coli MRE-600 ribosomes were synthesised and tested in a cell-free system without a template. In these substances the nucleic bases were linked covalently with the ribose residue or had a limited rotation about the glycosidic bond. 3'(2')-O-(N-formylmethionyl)-8-bromoadenosine 5'-phosphate and 3'(2')-O-phenylalanyl-8,5'-anhydro-8-mercaptoadenosine were shown to possess a high peptide donor and acceptor activity correspondingly. Contrary to that 3'(2')-O-phenylalanyl-8-bromoadenosine was practically inactive as a peptide acceptor and 3'(2')-O-(N-formylmethionyl)-8,5'-anhydro-8-mercaptoadenosine had no peptide donor activity at all. PMR and CD spectra of the compounds synthesised were investigated. The significance of conformation of the model substrates on their activity is discussed.
Mol Biol (Mosk)
PMID:[Peptidyl transferase center of ribosomes. I. Difference in the substrate specificity of the acceptor and donor portions]. 34 63

The reaction of 3'(2')-O-(N-formylmethionyl)-adenosine 5'-phosphate with Phe-tRNA or CACCA-Phe catalysed with E. coli MRE-600 ribosomes and stimulated with cytidine 5'-phosphate was investigated. It was shown that the reaction with Phe-tRNA was stimulated within 2--3 times when the temperature has been raised from 0 to 40 degrees. On the contrary when the peptide acceptor was CACCA-Phe the yield of peptides synthesis dropped 5 times and more under the same conditions. Similar temperature influence was observed in the reaction with 50S subunits. The inhibition of peptide bond formation with pA and CpA at 0 degrees was achieved up to 80--90% but it was very low at 40 degrees. The synthesis of tri- and tetrapeptides was observed when the reaction of 3'(2')-O-(N-formylmethionyl)-adenosine 5'-phosphate was carried out either with Phe-tRNA or with CACCA-Phe.
Mol Biol (Mosk)
PMID:[Peptidyltransferase center of ribosomes. II. Effect of temperature on the activity of model peptide donors and a study of oligopeptide formation in a matrix-free system with ribosomes]. 35 73

The transport systems (enzymeII-complexes of the PEP-dependent sugar:phosphotransferase system) coded for in the mtl and in the gut (srl) operon of E. coli K12 have been shown to be the pacemaker enzymes in the catabolism of the two hexitols D-mannitol and D-glucitol, respectively. As for other pacemaker enzymes their activity is regulated in a complex way: (i) via competitive inhibition by analogues. (ii) via non-competitive (feedback) inhibition by the simultaneous, rapid uptake of a number of structurally related or non-related carbohydrates, regardless if these are transported by group translocation, active transport or facilitated diffusion. This type of inhibition is strongly reinforced, if the inhibitory carbohydrates are converted efficiently into hexose-phosphates at the same time. Among these, predominantly D-fructose-6-P seems to act as a feedback inhibitor for the hexitol specific enzymeII-complexes: (iii) inhibition of hixitol-phosphate accumulation by D-glucose-6-P. The influence of additional parameters (PEP level, P approximately HPr level) and indications for the existence of further mechanisms controlling the activity of hexitol and other carbohydrate transport systems will be discussed, as will be the part the inhibitory mechanisms described above play in the phenomena of transient repression and inducer exclusion.
Mol Gen Genet 1978 Nov 16
PMID:Analysis of regulatory mechanisms controlling the activity of the hexitol transport systems in Escherichia coli K12. 36 87

Association of the apo-beta 2 and the holo-(beta-PLP)2 subunits of tryptophan synthase from Escherichia coli (L-serine hydro-lyase (adding indole) (EC 4.2.1.20)) with alpha subunits of the same enzyme has been studied by microcalorimetry. The results obtained from thermometric titrations clearly demonstrate that only the native complex alpha2beta 2 is formed, independent of an excess of alpha protein. The reaction of the holo-(beta-PLP)2 with alpha subunits at 25 degrees C is accompanied by a negative enthalpy change, which is almost twice as large as that for complex formation with the apo-beta 2 protein, thus indicating that the interaction enthalpy becomes more favorable in the presence of the coenzyme pyridoxal 5'-phosphate (PLP). Both reaction enthalpies show very large negative temperature coefficients, -3600 +/- 100 cal K-1 (Mol of beta 2)-1 being the value for the formation of the apoenzyme and -2300 +/- 100 cal K-1 (mol of beta 2)-1 pertaining to formation of the holoenzyme. The studies on the association of alpha and beta2 subunits in the two buffers revealed that at 25 degrees C approximately 0.75 proton are absorbed in the presence and absence of the coenzyme, whereas at 35 degrees C one proton is taken up from the solution when PLP is present, but two if the apo-beta 2 complex reacts. These results are a clear indication of energetic linkage between intersubunit interaction, hydrogen ion equilibria, and the binding of the coenzyme.
 ...
PMID:Subunit interaction in tryptophan synthase of Escherichia coli: calorimetric studies on association of alpha and beta 2 subunits. 37 96

The interaction of water molecules from the vapour phase with the total backer's yeast tRNA preparation was studied by the dynamic aquametric method. The primary hydration sites for processes of sorption and desorption of water molecules was evaluated by means of multilayer adsorption BET-equation. It was shown that the primary hydration sites are the oxygen atoms in the ribose-phosphate backbone of the tRNA molecule. The structure of surfaces of globular proteins and tRNA molecules were compared from the point of view of their ability to interact with water molecules. The higher degree of maximal hydration (under saturated water vapour or in aqueous solution) was considered as a result of regular arrangement of the most part of tRNA primary hydration sites.
Mol Biol (Mosk)
PMID:[Hydration of a preparation of total yeast tRNA]. 37 64

The plasmid pMY3, which was constructed so as to express the Su+7 amber suppressor tRNA gene, also relaxes control of stable RNA synthesis in stringent cells. The relaxation is not growth medium or strain-dependent and does not occur in the presence of the vehicle alone. When expression of the effective sequence is diminished, in a lysogen of phi 80d3 ilv+Su+7, the sequence no longer affects RNA synthesis. The relaxation is general, extending to all or almost all tRNA loci, including tRNAs located in the ribosomal spacer regions, and to all ribosomal RNAs. Relaxed plasmid-carrying strains are still able to elevate guanosine tetra- and penta-phosphate levels in response to amino acid starvation, but steady state levels are somewhat diminished. Aminoacyl-tRNA falls to control levels when the plasmid-carrying strain is deprived of amino acid. Therefore, the relaxed strain perceives amino acid starvation, but does not respond normally. These properties define a novel locus which relaxes stringent control.
Mol Gen Genet 1979 Mar 05
PMID:Relaxation of stable RNA synthesis by a plasmid-borne locus. 37 46

The present work is concerned with a sensitive and fast micromethod for separation of single- and double-stranded molecules of nucleic acid by hydroxyapatite (HAP) thin-layer chromatography. The thin layers were obtained by precipitation of ground HAP particules into the surface of the plates in water. Chromatography in sodium phosphate buffer makes it possible to separate from 1 to 50 micrograms of nucleic acids for 30--50 sec. Thereby double-stranded molecules remain at the starting line, whereas single-stranded DNA or RNA follow up the solvent. For quantitative assay of nucleic acids by HAP thin-layer chromatography, the plates were scanned in UV light, radioactivity was measured without extracting substances from HAP and DNA and RNA were eluted with the help of phosphate buffer. A simple and accurate determination method has been suggested consisting in dissolving HAP in perchloric acid followed by hydrolysis of nucleic acids and spectrophotometry of solutions. The retrieval of the material after chromatography in 99 +/- 2%, the mean determinations error is 2--3%. The conditions are described for extraction, after thin-layer chromatography, of desalted and concentrated DNA, ready for use in later experiments. The paper describes a method: for determination of the degree of DNA nativity; quantitative determination of DNA in solutions, containing admixtures; separation of synthesized RNA from its precursors and from the DNA template; assay of DNA thermostability; investigation of the kinetics of DNA reassociation and DNA-DNA hybridization. Some results obtained from hydroxyapatite thin-layer chromatography are discussed.
Mol Biol (Mosk)
PMID:[Hydroxyapatite thin-layer chromatography of nucleic acid]. 37 2

It has been shown that 50S subunits of E. coli MRE-600 ribosomes catalyze the reaction of N-(formyl)-methionyl ester of adenosine 5'-phosphate acting as peptide donor, with Phe-tRNA or CACCA-Phe serving as a peptide acceptor. The reaction is stimulated by cytidine 5'phosphate and inhibited by lincomycin, puromycin and chloramphenicol. The obtained results show that the structure of the donor site of peptidyltransferase is completely assembled on the 50S subunit and 30S subunit is not required for its formation.
Mol Biol (Mosk)
PMID:[Fragment reaction catalyzed by E. coli ribosomes]. 37 8

We have studied the effects of Co2+ and Mn2+ ions on the low-field nuclear magnetic resonance (NMR) spectra of pure class 1 transfer ribonucleic acid (tRNA) species. With 1.2 mM tRNA in the presence of 15 mM MgCl2 discrete paramagnetic effects were observed for Co2+ at concentrations in the range 0.02--0.1 mM and for Mn2+ in the range 0.002--0.01 mM, indicating fast exchange of these cations with tRNA. Both of these cations paramagnetically relax the s4U8--A14 resonance as well as other resonances from proximal base pairs. The Co2+ site appears to be the same site on G15 which was observed crystallographically [Jack, A., Ladner, J. E., Rhodes, D., Brown, R. S., & Klug, A. (1977) J. Mol. Biol. 111, 315-328]; the initially occupied tight Mn2+ site is the cation site involving the phosphate of U8. There are three base pairs within 10 A of both sites, namely, G15--C48, A14--s4U8, and C13--G22; this has led to the assignment of the G15--C48 and C13--G22 resonances in the NMR spectrum [Jack, A., Ladner, J. E., Rhodes, D., Brown, R. S., & Klug, A. (1977) J. Mol. Biol. 111, 315--328; Holbrook, S. R., Sussman, J. L., Warrant, R. W., Church, G. M., & Kim, Sung-Hou (1977) Nucleic Acids Res. 4, 2811--2820; Quigley, G. J., Teeter, M. M., & Rich, A. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 64--68].
 ...
PMID:Paramagnetic ion effects on the nuclear magnetic resonance spectrum of transfer ribonucleic acid: assignment of the 15--48 tertiary resonance. 38 41


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>