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

Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate anhydride to the hydroxyl groups of homopolyribonucleotides was investigated as a chemical model of the biochemical aminoacylation of tRNA. Imidazole catalyzed transfer of phenylalanine to poly(U) increases from pH 6.5 to 7.7 and decreases above pH 7.7. At pH 7.7 approximately 10% of the phenylalanyl residues are transferred to poly(U). At pH 7.1, transfer to poly(U) was five times as great as to poly(A) and transfer to a poly(A) poly(U) double helix was negligible. At pH 7.1 approximately 45 mole percent linkages to poly(U) were monomeric phenylalanine; the remainder of the linkages were peptides of phenylalanine. The number of linkages and their lability to base and neutral hydroxylamine indicates that phenylalanine and its peptides are attached as esters to the 2' hydroxyl groups throughout poly(U) and the 2' (3') hydroxyl groups at the terminus of poly(U). These results do model the contemporary process of aminoacyl transfer to tRNA and continue to suggest that a histidine residue is in the active site of aminoacyl-tRNA-synthetases.
J Mol Evol 1975 Dec 29
PMID:Aminoacyl transfer from an adenylate anhydride to polyribonucleotides. 0 44

1. The thermodynamics and molecular basis of energy-linked conformational changes in the cytochrome aa3 and ATP synthetase complexes of the mitochondrial membrane have been studied with spectrophotometrical and fluorometrical techniques. 2. Ferric cytochrome aa3 exists in two conformations, high spin and low spin, the equilibrium between these states being controlled by the electrical potential difference across the mitochondrial membrane. The conformational change is brought about by an electrical field-driven binding of one proton per aa3 to the complex. At pH 7.2 the concentration of the two conformations is equal at a membrane potential of 170 mV corresponding to about 4 kcal/mole. 3. The high to low spin transition in ferric aa3 is also induced by hydrolysis of ATP in which case two molecules of aa3 are shifted per ATP molecule hydrolyzed. This is in accordance with translocation of two protons across the mitochondrial membrane coupled to hydrolysis of ATP as proposed in the chemiosmotic theory of oxidative phosphorylation. 4. The conformational transition in cytochrome aa3 is not an expression of the formation of a 'high-energy' intermediate or reversal of the energy-transducing pathway of oxidative phosphorylation, but is presumably the basis of allosteric control of the activity of cytochrome oxidase by the energy state of the mitochondrion. This control is exerted by a regulatory mechanism in which the electrical potential difference controls the conformation and redox properties of the heme centres and thereby the rate of oxygen consumption. 5. The synthesis of one molecule of ATP by oxidative phosphorylation is energetically equivalent to the work done in carrying two electrical charges across the entire mitochondrial membrane. 6. Fluorescence changes of aurovertin bound to ATP synthetase reveal that the electrical membrane potential induces a conformational change in the F1 portion of the enzyme which is probably associated with dissociation of the natural F1 inhibitor protein. This conformational change is energetically equivalent to the work done in carrying one electrical charge across the mitochondrial membrane. 7. A model is proposed for the mechanism of the electrical field-induced conformational changes in the cytochrome aa3 and ATP synthetase complexes, and the significance of these changes in the mechanism and control of mitochondrial energy conservation is discussed.
Mol Cell Biochem 1976 Mar 26
PMID:Conformational changes in cytochrome aa3 and ATP synthetase of the mitochondrial membrane and their role in mitochondrial energy transduction. 0 67

The binding of nicotinamide adenine dinucleotide (NAD+) to yeast glyceraldehyde-3-phosphate dehydrogenase (GPDH) has been studied at pH 6.5 and 8.5, at 5,25, and 40 degrees C, by calorimetry, fluorometry, spectrophotometry, equilibrium dialysis, and flow dialysis. As reported earlier for pH 7.3 (Velick S.F., Baggott, J.P., and Sturtevant, J.M. (1971), Biochemistry 10, 779), the binding is accompanied by enthalpy changes which become rapidly more negative as the temperature increases, with delta Cp = -500 to -750 cal deg-1 (mole of NAD+ bound)-1, and by entropy changes which also, as required by the large negative delta Cp, become rapidly more negative with increasing temperature. The binding data at pH 6.5 can be fitted on the basis of either four identical noninteracting sites, or of four sites showing a small degree of negative cooperativity. The data at pH 8.5, particularly at 40 degrees C, require the introduction of positive cooperativity, as was previously shown by Kirschner et al. (Kirschner, K., Eigen, M., Bittman, R., and Voigt, B. (1966), Proc. Natl. Acad. Sci. U.S.A. 56, 1661), and can be equally well fitted on the basis of a sequential model (Adair, G.S. (1925), J. Biol. Chem. 63, 529) or a concerted model (Monod, J., Wyman, J., and Changeux, J.P. (1965), J. Mol. Biol. 12, 88). It is proposed that the observed thermodynamic changes are largely the result of a hydrophobic effect due to a decrease in the exposure of nonpolar groups to the solvent, and of a tightening of the protein structure when the coenzyme is bound with concomitant decrease in the number of easily excitable internal degrees of freedom.
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PMID:Energetics of the cooperative and noncooperative binding of nicotinamide adenine dinucleotide to yeast glyceraldehyde-3-phosphate dehydrogenase at pH 6.5 and pH 8.5. Equilibrium and calorimetric analysis over a range of temperature. 1 17

Amylase from chicken pancreas was purified by an affinity method involving filtering a crude extract from pancreas through a Sepharose-wheat albumin column and eluting the retained enzyme with maltose. The purified amylase showed two active bands upon polyacrylamide electrophoresis in an alkaline buffer system and only one band in an acidic buffer system. The enzyme is a Ca2+-glycoprotein which behaves as a typical alpha-amylase. It consists of a single polypeptide chain with molecular weight 53,000 and contains 5.3 moles of reducing sugars per mole of protein. Optimal conditions of pH and temperature for the enzymic activity are 7.5 and 37 degrees C. The enzyme is irreversibly inactivated by removal of Ca2+ by exhaustive dialysis and is activated by the presence in the assay mixture of Cl-; other halides are less effective than Cl- in activating the enzyme.
Mol Cell Biochem 1977 Aug 19
PMID:Purification and properties of alpha-amylase from chicken (Gallus gallus L.) pancreas. 2 May 68

Concentration dependence of the equivalent conductance of isoionic DNA solutions has been studied at different temperatures. The limiting equivalent conductance (lambda infinity) at every temperature investigated has been obtained by extrapolation to the infinite dilution in Kohlraush's plots. At the same time in plots c lambda c versus 1/lambda c (lambda c is equivalent to conductance at the concentration c), corresponding to the linear form of Ostwald's dilution law, the straight lines were obtained. Both lambda infinity and acidity constants (K) have been determined from these plots. The values of lambda infinity by two methods are in well agreement. The average values of lambda infinity were used for energy activation of conductivity calculation, equal to 2,40 +/- 0,05 kcal/mole. The acidity constant of primary phosphoryl groups passes through a maximum near 33 degrees. Equivalent conductance of hydrogen ions calculated by neglecting of macroion's mobility and by using of potentiometric determined concentration (cH+) has been shown to increase with cH+. Unusual behavior of DNA in isoionic solutions is discussed.
Mol Biol (Mosk)
PMID:[Temperature dependence of conductance of isoionic DNA solutions. Determination of dissociation constants of primary phosphoryl groups]. 3 37

NAD(P)H: FMN oxidoreductase (flavin reductase) couples in vitro to bacterial luciferase. This reductase, which is also postulated to supply reduced flavin mononucleotide in vivo as a substrate for the bioluminescent reaction, has been partially purified and characterized from two species of luminous bacterial. From Photobacterium fischeri the enzyme has a M. W. determined by Sephadex gel filtration, of 43,000 and may have a subunit structure. The turnover number at 20 degrees C, based on a purity estimate of 20 percent, is 1.7 times 10-4 moles of NADH oxidized per min per mole of reductase. The reductase isolated from Beneckea harveyi has an apparent molecular weight of 23,000; its purity was too low to permit estimation of specific activity. Using a spectrophotometric assay at 340 nm with the P. fischeri reductase, both NADH (Km, 8 times 10-5 M) and NADPH (Km, 4 times 10-4 M) were enzymatically oxidized, the Vmax with NADH being approximately twice that of NADPH. Of the flavins tested in this assay, only FMN (Km, 7.3 times 10-5 M) and FAD (Km, 1.4 times 10-4 M) were effective, FMN having a Vmax three times that of FAD. In the coupled assay, i.e., measuring the bioluminescence intensity of the reaction with added luciferase, the optimum FMN concentration was nearly 100 times less than in the spectrophotometric assay. The studies reported suggest the existence of a functional reductase-luciferase complex.
Mol Cell Biochem 1975 Jan 31
PMID:Flavin mononucleotide reductase of luminous bacteria. 4 4

Virginiamycin S (VS, a type B component of the synergistin group of antibiotics) is fluorescent in solution: the fluorescence intensity is proportional to VS concentration. The intensity of VS fluorescence was found to increase upon addition of 50S ribosomal subunits, and this variation (deltaI 416 nm) to be proportional to the concentration of 50S subunits. This new technique was, then, used to measure the binding reaction of VS to ribosomes. Similar patterns of linkage were obtained for ribosomes and large subunits, whereas very little fixation to 30S particles was detected. The binding reaction was virtually instantaneous at any temperature, and, for saturating VS, was not influenced by Mg++ concentration in the range 1 to 20 mM, nor by the replacement of 100 mM K+ with NH+4. The association constant of VS TO 50S particles was found to be KA=2.5 X 10(6)M-1, and from the Scatchard plot a v value of 0.9 was calculated, which points to a stoichiometric reaction leading to 1 mole VS bound per mole of 50S particles. Upon fixation of virginiamycin M (VM, a type A component of the synergistin group of antibiotics), the delta I of the VS-ribosome complex was increased, and a KA=15 x 10(6)M-1 was recorded for the association constant of VS to 50S particles. Such sixfold increase in the affinity of ribosomes for VS may account for the synergistic effect of the 2 virginiamycin components in sensitive bacteria.
Mol Gen Genet 1978 Oct 25
PMID:A spectrofluorimetric study of the interaction between virginiamycin S and bacterial ribosomes. 10 39

A macromolecular component binding 3H-labelled 17 beta-oestradiol in a specific manner and sedimenting in the 8-10-S region on sucrose gradient has been detected in the mammary gland cytosol of ovariectomized adult virgin mice. The dissociation constant of the macromolecule-oestradiol complex is 4.2 times 10(-10)M at 4 degrees C. The binding sites for 17beta-oestradiol of cytosol are 3.7 times 10(-14) mole/mg of protein. Incubation of cytosol with different enzymes suggests that the oestrogen-binding cytosol component is proteinaceous. The binding activity is destroyed by incubation at high temperatures and by some but not all SH-reagents tested. Competition studies show a specificity for oestrogens relative to other steroid hormones. The conclusion is that mammary gland cytosol of virgin mice contains oestradiol receptor. The receptor content does not increase in a specific manner during pregnancy and lactation but rather proportionally to total mammary gland protein.
Mol Cell Endocrinol
PMID:Oestrogen receptor in mammary gland cytosol of virgin, pregnant and lactating mice. 17 90

Specific modification of the monomeric fraction III of ferri-hemoglobin from insect larvae Chironomus thummi thummi (Hb CTT) was studied on histidyl residues His-G19 (pK 4,8), His-E5 (pK 7,3) and Met-H22 at different pH using iodacetamide and spin label 2,2,6,6-tetramethyl-4-bromacethyl-piperidin-1-oxyl, an analogue of bromacetate. The analysis of the products of carboxymethylation (CM) showed that at pH 5,0 two products of modification CM-(His-G19)-Hb CTT, and CM-(Met-H22)-Hb CTT were obtained. In the case of modification at pH 7,2 with a spin label dicarboxymethylatid product CM-(His-G19)-CM (His-E5)-Hb CTT is obtained. In all products the degree of modification was one spin label per mole protein. Based on the data on the primery and tertiary structures Hb CTT and the results of the investigation, different reactivity of His-G19 and His-E5, as well as the cause of the absence of the product of carboxymethylation on His-G2 have been discussed. By analizing the absorption spectra of carboxymethylated derivatives of hemoglobin in the ultraviolet and visible region, as well as from the pH dependence curves of the absorption at Soret band in the interval pH 5,5-11,5 it has been shown that carboxymethylation of His-G19 and His E5 is not accompanied by any substantial disturbance of the structures of aquous-complexes Hb CTT. Modification of Met-H22 leads to strong changes in the absorption spectrum and to the absence of pH dependence of the absorption at Soret band, which indicates a change in the aquous-complexes Hb CTT structure.
Mol Biol (Mosk)
PMID:[Selected carboxymethylation of ferri-hemoglobin from insect larvae Chironomus thummi thummi]. 17 63

The binding of [125I]hCG to immature and mature follicles and corpora lutea of goat ovaries has been studied. The hormone is bound maximally by corpora lutea although mature follicles also exhibit some binding. Immature follicles are practically devoid of receptors for this hormone. In the corpus luteum, the receptors for the hormone are present in thecal and luteal cells. Autoradiographic studies show the location of the bound radioactivity grains primarily along the plasma membranes of these cells, although some radioactivity grains were also seen in the cytoplasm of luteal but not thecal cells. On a mole to mole basis, hCG was found to displace [125I]hCG from binding to receptors on corpus luteum better than hLH and oLH.
Mol Cell Endocrinol 1976 Dec
PMID:Ontogenesis, distribution and relative sensitivity of hCG receptors to hCG and LH in goat ovaries. 18 5


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