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)

X-ray diffraction difference electron density maps at 3 A resolution obtained from di and tetra-ligated T-state hemoglobin (Hb) crystals are reported. Crystals isomorphous with native deoxyhemoglobin were obtained from ammonium sulfate solutions incubated with the synthetic allosteric effector RSR-56. RSR-56 binds at two symmetry-related Hb central water cavity sites and each molecule has major interactions with three different subunit side-chains; one effector with Arg141 alpha 2 HC3, Lys99 alpha 1 G6 and Asn108 beta 1 and the other with the symmetry related residues, Arg141 alpha 1 Lys99 alpha 2 and Asn108 beta 2. Crystals mounted in a nitrogen filled glove box were di-ligated as previously found with polyethyleneglycol Hb crystals. Crystals mounted in air under a layer of mother liquor were bright red and showed all four heme groups ligated. The difference electron density from the di-ligated crystals showed atomic movements to be restricted to the immediate neighborhood of the heme groups and the allosteric effector. By contrast, the tetra-ligated structure showed extended difference electron density near amino acid residues around both alpha and beta heme groups and along the alpha 1/beta 2 interface. Ligation of the beta heme group appears to magnify the difference density around the alpha heme groups. There is no evidence of breakage of the Bohr salt bridge, His146 beta HC3----Asp94 beta FG1, in the crystal. The observed difference electron density maps may help to clarify the way the allosteric mechanism is triggered.
J Mol Biol 1992 Sep 20
PMID:X-ray diffraction study of di and tetra-ligated T-state hemoglobin from high salt crystals. 140 65

Methane monooxygenase is a multicomponent enzyme system that catalyzes the conversion of methane to methanol in methanotrophic bacteria. Catalysis occurs at non-heme dinuclear iron centers contained in the hydroxylase component of the system, a dimer of composition alpha 2 beta 2 gamma 2. The hydroxylase protein from Methylococcus capsulatus (Bath) has been crystallized from aqueous solutions containing polyethylene glycol, lithium sulfate, and ammonium acetate. The crystals are orthorhombic, space group P2(1)2(1)2(1), with one dimer of relative molecular mass M(r) = 252,000 in the asymmetric unit. The unit cell dimensions are a = 62.6 A, b = 110.1 A, c = 333.5 A. The crystals diffract uniformly beyond 2.5 A resolution. Crystals of the related hydroxylase from Methylosinus trichosporium OB3b have also been obtained.
J Mol Biol 1992 Sep 20
PMID:Crystallization and preliminary X-ray analysis of the methane monooxygenase hydroxylase protein from Methylococcus capsulatus (Bath). 140 75

In Chlamydomonas reinhardtii, expression of the cabII-1 gene increases dramatically in response to light (cabII-1 encodes one of the light-harvesting chlorophyll a/b-binding proteins of photosystem II). We have used a region upstream of the cabII-1 gene in translational fusions to the bacterial uidA gene (encodes beta-glucuronidase) and transcriptional fusions to the Chlamydomonas nitrate reductase gene (nit1). Chlamydomonas transformants carrying intact copies of the chimeric uidA gene do not express beta-glucuronidase at the level of enzyme activity or mRNA accumulation. Methylation in the cabII-1 promoter region of the introduced gene is extensive in these strains, suggesting that newly introduced foreign genes may be recognized and silenced by a cellular mechanism that is correlated with increased methylation. Transformants that express the chimeric cabII-1/nit1 gene have been recovered. In contrast to the endogenous nit1 gene, the chimeric cabII-1/nit1 gene is expressed in ammonium-containing medium. Moreover, nit1 mRNA accumulation is dramatically stimulated by light, with a time course that is indistinguishable from that of the endogenous cabII-1 gene. The cabII-1/nit1 gene has been used to select transformants in a nit1- nit2- Chlamydomonas strain (CC400G) and should be useful for transformation of the large number of mutants in the Ebersold-Levine lineage, which carry the same mutations.
Mol Cell Biol 1992 Nov
PMID:Expression of chimeric genes by the light-regulated cabII-1 promoter in Chlamydomonas reinhardtii: a cabII-1/nit1 gene functions as a dominant selectable marker in a nit1- nit2- strain. 140 96

NADPH cytochrome c (P-450) reductase was purified from human placental microsomes using a combination of affinity and gel filtration chromatography. Affinity chromatography using agarose-hexane-adenosine 2'5 diphosphate resulted in two protein bands being detected by SDS-PAGE of approximate MwS 68 and 75 kDa. Fractions containing the two proteins were pooled, and then resolved using Sephacryl S-200. Both of the purified proteins displayed enzyme activity, measured by their ability to reduce cytochrome c. The 75 kDa protein obtained was used to immunize three female New Zealand white rabbits. The IgG fraction was partly purified from rabbit sera which suppressed placental microsomal NADPH cytochrome c reductase activity by > 80% using 33% ammonium sulphate. The procured antibody suppressed androstenedione aromatase activity in microsomal preparations of human placental and breast adipose tissue, and NADPH cytochrome c reductase activity in prostate (benign and malignant), MDA-MB-231 breast cancer cells, breast adipose, Hep G2 hepatoma cells and placental microsomal preparations. The extent of NADPH cytochrome c reductase inhibition varied in the order of malignant prostate < benign prostate < MDA < breast adipose < Hep G2 < placenta. The results suggest that human placental NADPH cytochrome c (P-450) reductase shares common antigenic epitopes pertinent to its capability of reducing cytochrome c in all of the above-mentioned tissues. In attempting to associate possible changes in NADPH cytochrome c reductase activity imposed by neoplasia to the obtained immunochemical cross reactivity and enzyme activity results, it was noted that microsomes obtained from MDA cells exhibited enzyme activity significantly less than that of breast adipose microsomes (1.6 and 8.1 nmol/min/mg protein, respectively) and by comparison showed 6% less homology towards the placental antibody. The results obtained for benign and malignant prostate showed no significant difference between the neoplastic states as adjudged by enzyme activity and immunochemical assays.
J Steroid Biochem Mol Biol 1992 Nov
PMID:Immunochemical specificity of placental NADPH cytochrome c (P-450) reductase in neoplastic and non-neoplastic human tissue. 141 86

The molecular structure of an insect fatty-acid-binding protein isolated from Manduca sexta L. has been determined and refined to a nominal resolution of 1.75 A. Crystals used in the investigation were grown from 1.6 M-ammonium sulfate solutions buffered at pH 4.5 with 50 mM-sodium succinate, and belonged to space group P2(1) with unit cell dimensions of a = 27.5 A, b = 71.0 A, c = 28.7 A and beta = 90.8 degrees. An electron density map, phased with four heavy-atom derivatives and calculated to 2.5 A resolution, allowed for complete tracing of the 131 amino acid residue polypeptide chain. Subsequent least-squares refinement of the model reduced the R-factor from 46.0% to 17.3% using all measured X-ray data from 30.0 A to 1.75 A. Approximately 92% of the amino acid residues fall into classical secondary structural elements including ten strands of anti-parallel beta-pleated sheet, two alpha-helices, one type I turn, three type II turns, four type II' turns and one type III turn. As in other fatty-acid-binding proteins, the overall molecular architecture of the insect molecule consists of ten strands of anti-parallel beta-pleated sheet forming two layers that are nearly orthogonal to one another. A helix-turn-helix motif at the N-terminal portion of the protein flanks one side of the up-and-down beta-barrel. The functional group of the fatty acid is within hydrogen-bonding distance of Gln39, Tyr129, Arg127 and a sulfate molecule, while the aliphatic portion of the ligand is surrounded by hydrophobic amino acid residues lining the beta-barrel. The binding of the carboxylic acid portion of the ligand is very similar to that observed in P2 myelin protein and the murine adipocyte lipid-binding protein, but the positioning of the hydrocarbon tail after approximately C6 is completely different.
J Mol Biol 1992 Nov 05
PMID:Crystallization, structure determination and least-squares refinement to 1.75 A resolution of the fatty-acid-binding protein isolated from Manduca sexta L. 144 82

The objective of this study is to quantify the contributions of cations, anions and water to stability and specificity of the interaction of lac repressor (lac R) protein with the strong-binding symmetric lac operator (Osym) DNA site. To this end, binding constants Kobs and their power dependences on univalent salt (MX) concentration (SKobs = d log Kobs/d log[MX]) have been determined for the interactions of lac R with Osym operator and with non-operator DNA using filter binding and DNA cellulose chromatography, respectively. For both specific and non-specific binding of lac R, Kobs at fixed salt concentration [KX] increases when chloride (Cl-) is replaced by the physiological anion glutamate (Glu-). At 0.25 M-KX, the increase in Kobs for Osym is observed to be approximately 40-fold, whereas for non-operator DNA the increase in Kobs is estimated by extrapolation to be approximately 300-fold. For non-operator DNA, SKobsRD is independent of salt concentration within experimental uncertainty, and is similar in KCl (SKobs,RDKCl = -9.8(+/- 1.0) between 0.13 M and 0.18 M-KCl) and KGlu (SKobs,RDKGlu = -9.3(+/- 0.7) between 0.23 M and 0.36 M-KGlu). For Osym DNA, SKobsRO varies significantly with the nature of the anion, and, at least in KGlu appears to decrease in magnitude with increasing [KGlu]. Average magnitudes of SKobsRO are less than SKobsRD, and, for specific binding decrease in the order [SKobsRO,KCl[>[SKobsRO,KAc[>[SKobsRO,KGlu[ . Neither KobsRO nor SKobsRO is affected by the choice of univalent cation M+ (Na+, K+, NH4+, or mixtures thereof, all as the chloride salt), and SKobsRO is independent of [MCl] in the range examined (0.125 to 0.3 M). This behavior of SKobsRO is consistent with that expected for a binding process with a large contribution from the polyelectrolyte effect. However, the lack of an effect of the nature of the cation on the magnitude of KobsRO at a fixed [MX] is somewhat unexpected, in view of the order of preference of cations for the immediate vicinity of DNA (NH4+ > K+ > Na+) observed by 23Na nuclear magnetic resonance. For both specific and non-specific binding, the large stoichiometry of cation release from the DNA polyelectrolyte is the dominant contribution to SKobs. To interpret these data, we propose that Glu- is an inert anion, whereas Ac- and Cl- compete with DNA phosphate groups in binding to lac repressor. A thermodynamic estimate of the minimum stoichiometry of water release from lac repressor and Osym operator (210(+/- 30) H2O) is determined from analysis of the apparently significant reduction in [SKobsRO,KGlu[ with increasing [KGlu] in the range 0.25 to 0.9 M. According to this analysis, SKobs values of specific and non-specific binding in KGlu differ primarily because of the release of water in specific binding. In KAc and KCl, we deduce that anion competition affects Kobs and SKobs to an extent which differs for different anions and for the different binding modes.
J Mol Biol 1992 Nov 05
PMID:Thermodynamic stoichiometries of participation of water, cations and anions in specific and non-specific binding of lac repressor to DNA. Possible thermodynamic origins of the "glutamate effect" on protein-DNA interactions. 144 86

Crystals of phosphoribosylaminoimidazolesuccinocarboxamide synthase (EC 6.3.2.6) from the yeast Saccharomyces cerevisiae were grown by the vapor diffusion hanging-drop technique, using ammonium sulfate as the precipitant. The crystals had dimensions up to 1.2 mm. X-ray diffraction experiments indicated a space group of P2(1)2(1)2(1) and unit cell parameters of a = 62.3 A, b = 63.5 A and c = 80.9 A, with one molecule in the asymmetric unit. Native data have been collected to 2.5 A resolution.
J Mol Biol 1992 Nov 05
PMID:Crystallization and preliminary X-ray investigation of phosphoribosylaminoimidazolesuccinocarboxamide synthase from the yeast Saccharomyces cerevisiae. 144 88

Several aspects of Mg2+ homeostasis were investigated in cultured chicken heart cells using the fluorescent Mg2+ indicator, FURAPTRA. The concentration of cytosolic Mg2+ ([Mg2+]i) is 0.48 +/- 0.03 mM (n = 31). To test whether a putative Na/Mg exchange mechanism controls [Mg2+]i below electrochemical equilibrium, we manipulated the Na+ gradient and assessed the effects on [Mg2+]i. When extracellular Na+ was removed, [Mg2+]i increased; this increase was not altered in Mg-free solutions, but was attenuated in Ca-free solutions. A similar increase in [Mg2+]i, which was dependent upon extracellular Ca2+, was observed when intracellular Na+ was raised by inhibiting the Na/K pump with ouabain. These results do not provide evidence for Na/Mg exchange in heart cells, but they suggest that Ca2+ can modulate [Mg2+]i. In addition, removing extracellular Na+ caused a decrease in intracellular pH (pHi), as measured by pH-sensitive microelectrodes, and this acidification was attenuated when Ca2+ was also removed from the solution. These results suggest that Ca2+ and H+ interact intracellularly. Since changes in the Na+ gradient can also alter pHi, we questioned whether pH can modulate [Mg2+]i. pHi was manipulated by the NH4Cl prepulse method. NH4(+)-evoked changes in pHi, as measured by the fluorescent indicator BCECF, were accompanied by opposite changes in [Mg2+]i; [Mg2+]i changed by -0.16 mM/unit pH. These NH4(+)-evoked changes in [Mg2+]i were not caused by movements of Mg2+ or Ca2+ across the sarcolemma or by changes in cytosolic Ca2+. Additionally, pHi was manipulated by changing extracellular pH (pHo).(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1992 Sep 08
PMID:Magnesium homeostasis in cardiac cells. 146 Dec 62

An endoglucanase I (EG1) from a fungal source (Humicola insolens) has been crystallized in a number of forms suitable for X-ray diffraction analysis. Four crystal forms have been grown from various precipitants using vapour phase diffusion methods in hanging drops. Three of these crystal forms diffract to beyond 2.5 A resolution. Two forms, obtained from ammonium sulphate at pH 5.4, or 8.0, grow as tetragonal bipyramids in space group P4(1)22 or P4(3)22, with approximate cell dimensions a = b = 102 A, c = 282 A. The other crystal forms were grown from polyethylene glycol 8000 at pH 8.0. One grows as monoclinic plates, space group P2(1), with cell dimensions a = 66.9 A, b = 75.2 A, c = 86.9 A and beta = 102.9 degrees and the other as long hexagonal rods in space group P6(1)22 or P6(5)22, with cell dimensions a = b = 119 A, c = 83 A.
J Mol Biol 1992 Dec 05
PMID:Crystallization and preliminary X-ray analysis of a fungal endoglucanase I. 146 28

High yields of toxic shock syndrome toxin-1, from Staphylococcus aureus, have been purified (> 99%) using a novel, simple, two-step procedure involving dye ligand chromatography. Crystals suitable for X-ray diffraction work were obtained by vapour diffusion using ammonium sulphate and polyethylene glycol as precipitants. They belong to the orthorhombic space group C222(1), with unit cell dimensions a = 108.6 A, b = 177.6 A and c = 97.5 A, with three molecules per asymmetric unit. The crystals diffract to at least 2.5 A resolution and are suitable for three-dimensional X-ray structural analysis.
J Mol Biol 1992 Dec 05
PMID:Purification, crystallization and preliminary X-ray analysis of toxic shock syndrome toxin-1 from Staphylococcus aureus. 146 31


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