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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe fibre diffraction studies on the interaction of DNA with different amino acids and peptides. The B form of DNA, with ten base-pairs per turn, is always found at high levels of humidity. We suggest that this pitch is observed because the DNA molecules are maintained in a straight position. In solution, the DNA molecules are bent and may have a larger pitch. The A form of DNA is never found upon dehydration. Instead, the B form may be either stabilized by the counterions or altered so that the number of base-pairs per helical turn decreases upon dehydration. Alteration is favoured either by small counterions that have a single charge or by large basic polypeptides and proteins. Stabilization is favoured by small counterions that have several charged groups. A third type of behaviour is found with some amino acids that contain hydrophobic groups, which destabilize the secondary structure of DNA, probably due to a modification of its intramolecular interactions. We have not detected any specific effect of amino acid side-chains, although the amino acid sequence has a clear influence on the interaction. We think that these observations are of interest in the pursuit of more detailed crystallographic studies on protein-DNA interactions.
J Mol Biol 1986 Feb 05
PMID:Influence of amino acid and peptide counterions on the conformation of DNA. 370 70

A dimyristoylphosphatidylcholine multilamellar system with varied water content was prepared by dessiccating sonicated vesicles in vacuo. The water content in the sample was determined by gas chromatography after dissolving the multilamellar system in water-free benzene. Differential scanning microcalorimetry revealed several endothermic peaks in the heating scan at subzero temperature, ranging from -25 to -3 degrees. The peaks that appeared in the subzero temperature range indicate the existence of water molecules bound to the lipid head groups, differing from free water that freezes at 0 degrees. The difference between the amount of water molecules that froze in calorimetry and the total amount of water detected by gas chromatography indicates the presence of unfreezable, tightly bound water molecules. The relative amount of free, intermediate, and unfreezable water was estimated by comparing the differential scanning microcalorimetry data with gas chromatography measurements. The addition of halothane and 1-hexanol significantly decreased the intermediately bound water peaks. The anesthetics dehydrated the lamellar system. The phase polymorphism of partially hydrated phospholipid multilayers is well known, and the temperature that corresponds to the main phase transition of fully hydrated lipid membranes shifts to a higher temperature. The addition of anesthetics increased the phase transition temperature when the water content was less than 18 wt%. This result is the complete reverse of the depressant action of anesthetics in fully hydrated lipid membranes. The present anesthetic effect upon the elevation of the transition temperature is apparently caused by anesthetic-induced dehydration of the lipid-water interface at the present experimental condition.
Mol Pharmacol 1986 Jun
PMID:Anesthetics release unfreezable and bound water in partially hydrated phospholipid lamellar systems and elevate phase transition temperature. 371 2

Using X-ray diffraction we have studied fibres obtained from complexes of DNA with lysine-rich polypeptides and with proteins that have different conformations, to ascertain whether the conformations of the polypeptides and the DNA are maintained upon interaction. Substances investigated include N-acetyl-Lys-Ala-Tyr-Ala-Lys-ethylamide, random poly(Leu50, Lys50), sequential poly(Leu-Lys), poly(Val-Lys), poly(Ala-Lys), poly(Lys-Ala-Ala-Lys), poly(Lys-Ala-Ala), poly(Lys-Leu-Ala), poly(Lys-Ala-Gly), protein phi 0 from sea cucumber spermatozoa, histone H1 and two fragments of this protein obtained by chemical cleavage. In general, the B form of DNA with ten base-pairs per helical turn is maintained upon interaction at high levels of humidity. The A form is never observed; it appears to be forbidden in a protein environment. No evidence for transition into any novel DNA conformation has been observed, although the B form is altered in some cases, in particular upon dehydration. Such alteration occurs always in the sense of tightening the double helix, so that the number of base-pairs per helical turn diminishes. The polypeptides may interact with DNA in both the alpha and beta conformations. We have found different types of complexes in which either a monolayer or a double layer of beta-pleated sheets is intercalated between layers of DNA molecules. Alternatively, the polypeptide chain may be wrapped around the DNA, following one of the grooves. The polypeptide conformation may be either maintained or changed upon interaction. The charge density of the polypeptide is an important parameter of the interaction. When it matches the charge density of the DNA, the polypeptide conformation is maintained in most cases; otherwise it is modified. The globular part of histone H1 gives a unique X-ray pattern upon interaction, indicative of a loss of order of DNA in the complex. On the other hand, the C-terminal part of histone H1 gives a very well-ordered complex, similar to a nucleoprotamine, in spite of its lower charge density.
J Mol Biol 1985 Sep 20
PMID:Interaction of DNA with lysine-rich polypeptides and proteins. The influence of polypeptide composition and secondary structure. 393 57

Metabolism of 7-chlorobenz(a)anthracene (7-Cl-BA) by liver microsomes from untreated rats, and from rats pretreated with either 3-methylcholanthrene or phenobarbital was studied. The metabolites were isolated by HPLC and characterized by UV-visible, mass, and proton NMR spectral analyses and identified as 7-Cl-BA trans-3,4-, 5,6-, and 8,9-dihydrodiols, 3-hydroxy-7-Cl-BA, and 4-hydroxy-7-Cl-BA. Proton NMR spectral analysis indicated that 7-Cl-BA trans-3,4-dihydrodiol preferentially adopted a quasidiequatorial conformation while trans-5,6- and 8,9-dihydrodiols preferentially adopted a quasidiaxial conformation. Comparison of circular dichroism spectra with those of 7-bromobenz(a)anthracene trans-dihydrodiol metabolites of known absolute stereochemistry indicated that the major enantiomeric 7-Cl-BA trans-3,4-, 5,6-, and 8,9-dihydrodiols had R,R absolute configuration. Application of chiral stationary phase HPLC for direct resolution of the trans-dihydrodiols and their hydrogenated and dechlorinated derivatives enabled determination of the optical purity of each dihydrodiol metabolite obtained from the three microsomal systems. In vitro incubation of 7-Cl-BA under molecular oxygen-18 produced 7-Cl-BA trans-3,4-, 5,6-, and 8,9-dihydrodiols, each containing one oxygen-18 atom. Mass spectral analysis of the dehydration products of the oxygen-18-containing trans-dihydrodiol metabolites indicated that 7-Cl-BA 3S,4R-epoxide and 7-Cl-BA 8R,9S-epoxide were the predominant enantiomeric intermediates.
Mol Pharmacol 1985 Jul
PMID:Stereoselective metabolism of 7-chlorobenz(a)anthracene by rat liver microsomes. Absolute configurations and optical purities of trans-dihydrodiol metabolites. 402 98

Temperature dependence of spin-spin proton relaxation times of DNA and bound water and the content of bound water in the samples of DNA, saturated with water in the atmosphere with different relative humidities from 0 to 100% were studied by means of pulsed NMR. It is shown that the temperature transition in the system of DNA-bound water in the interval 18-35 degrees is observed only when the relative humidity is more than 70% and the double-stranded structure of DNA exists. The transition of DNA from one conformation into another passes through some intermediate state more labile and probably less ordered. This transition is accompanied by changes in the structure of the hydration shell. In the case when relative humidity is greater than 80%, the partial dehydration of DNA stimulated by the transition is observed. This dehydration increases with the increase of relative humidity.
Mol Biol (Mosk)
PMID:[NMR study of the structural transition in the DNA-bound water system in the interval of physiological temperatures]. 404 32

A comparison is made of the published data on different physical methods concerning small-scale (small-amplitude) thermal motions, conformers and conformational substates of myoglobin and some other proteins in crystal and solution. Because of the underestimation of the statical and dynamical rotational disorder of the crystal lattice, the X-ray diffraction method may somewhat overestimate the amplitude values of the intramolecular thermal motions, which leads to the underestimation of the extent of conformational rigidity of the protein molecule. In solution the rigid-body rotation of the macromolecules makes a significant contribution to the apparent amplitude of atomic displacement. The damping of these motions upon the increase of viscosity or freezing of solution, crystallization or intramolecular crosslinking can partially simulate the depression of intramolecular thermal motions. According to infrared spectroscopy data the crystallization of carboxymyoglobin as well as temperature decrease down to 5K are not accompanied by preferential stabilization of one of the several discrete conformers of the active site or by diminished distribution breadth of conformational substates within individual conformers. The structural differences between these discrete conformers and the more so between conformational substates are not sizable and are confined within a limit of the amplitude of thermal motion in the polymeric monocrystal including their paracrystalline regions. The dehydration of the hemoglobin and myoglobin films leads to the loss of conformational rigidity of the active site and to the distortion of its native conformation, i.e. to the inactivation of protein.
Mol Biol (Mosk)
PMID:[Thermal movements of proteins: small-scale fluctuation and conformation substates]. 635

The "energy-rich" thioester, N-acetyl-S-lactoylcysteine, is formed under anaerobic conditions from glyceraldehyde and N-acetylcysteine at ambient temperature in aqueous solutions of sodium phosphate (pH 7.0). The conversion of glyceraldehyde to lactoyl thioester occurs at a rate of about 0.4%/day in reactions with 10 mM glyceraldehyde, 10 mM thiol, and 500 mM sodium phosphate (pH 7.0). Thioester formation proceeds at an estimated efficiency of 76%, since a similar reaction with 12.5 mM thiol yields 50.7% lactate at 6 months from only 66.5% of the glyceraldehyde (or its isomer, dihydroxyacetone). The formation of lactoyl thioester most likely occurs by the phosphate-catalyzed dehydration of glyceraldehyde to give pyruvaldehyde, which combines with thiol to form a hemithioacetal that rearranges to the thioester. A second energy-rich thioester, N-acetyl-S-glyceroylcysteine, is also produced from glyceraldehyde when these reactions are carried out in the presence of oxygen and to a limited extent in the absence of oxygen. In the presence of oxygen the formation of glyceroyl thioester continues until the thiol disappears completely by oxidation. The significance of these reactions to the energetics of the origin of life is discussed.
J Mol Evol 1984
PMID:Nonenzymatic formation of "energy-rich" lactoyl and glyceroyl thioesters from glyceraldehyde and a thiol. 643 34

Effects of dehydration on the quantum yield of charge separation in the reaction centres, fluorescence and nanosecond recombination luminescence in R. rubrum chromatophores have been investigated. It has been shown that dehydration results in more than a 10 times decrease in the quantum efficiency of photosynthesis. Besides, photoinduced fluorescence changes practically disappear in dehydrated samples and the parameters of nanosecond luminescence substantially change. These observations indicate that strong dehydration causes a deterioration of the primary charge separation process at the early picosecond stages of excitation energy transduction into energy of separated charges. This is, probably, due to either changes in the dynamic characteristics of the reaction centre pigment-protein complex or alteration in the structure state (spacings and mutual orientations) of the primary reactants involved in the primary charge separation.
Mol Biol (Mosk)
PMID:[Effect of dehydration on the primary picosecond stages of charge separation in Rhodospirillum rubrum]. 644 Nov 14

Exposure of pea chloroplasts to electric field causes the appearance of a new thermoluminescence (TL) band at--(40-50) degrees C and a reduction of the intensity of its main bands. Extents of intensity drop are different for different components of TL and depend on the temperature of illumination. The charge traps responsible for the individual TL components seem to be localized in microsurroundings having different field susceptibility. The electric field effects observable at different temperatures are in correlation with the thermodepolarization currents which reflect the mobility and number of charged groups undergoing a field-induced displacement in chloroplast membranes. Dehydration. of chloroplast film preparations causes a reduction in the intensities of the TL peaks and thermodepolarization currents and a shift of the peaks positions toward higher temperatures. It is assumed that the traps of the recombining charges have two different conformations, each with its own frequency factor for the recombination reaction. Changes in the thermoluminescence behavior in applied electric field are due to the polarization of the traps, which increases the existence probability of a conformation with a high frequency factor.
Mol Biol (Mosk)
PMID:[Thermoluminescence and electric polarization in chloroplasts]. 647 74

The pH and ionic strength dependence of the states of aggregation of brome mosaic virus protein has been investigated by small angle neutron scattering, quasielastic light-scattering, analytical centrifugation and electron microscopy. At pH above neutrality, protein oligomers are found in dynamical equilibrium, comprising monomers, dimers and aggregates of higher molecular weight. By lowering the pH, capsids assemble spontaneously with dimensions in solution which depend on ionic strength. If formed by dialysis, they contain 180 monomers, but are 30 A larger in diameter than the native virus. If formed by pH-jump, they contain less monomers: the deficiency decreases with decreasing the final pH and the initial protein concentration. Upon dehydration for electron microscopy, capsids contract by 10%.
J Mol Biol 1983 Mar 15
PMID:Self-assembly of brome mosaic virus protein into capsids. Initial and final states of aggregation. 684


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