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)

Native protein L7 from E. coli ribosomes, oxidized protein and a fragment of protein L7 containing the sequence 27--120 obtained by cleavage of the native protein by cyanogen bromide were investigated by sedimentation analysis. It was found that protein L7 exists in solution in a dimer form while the protein oxidized by hydrogen peroxide and the fragment 27--120 do not form a dimer. On the basis of these investigations a conclusion is made that the ability for dimerization is stimulated by N-terminal regions of the protein L7 molecule.
Mol Biol (Mosk)
PMID:[Role of the N-terminal sequence (1-26) in the dimerization of protein L7 in solution]. 37 54

The complexex DNA-Ag1+, DNA-Cu1+, protonated DNA and DNA methylated at N7 of guanine were oriented by pumping the solutions through a multicapillary cell in the direction of a light beam. The CD components along the DNA axis, delta epsilon parallel, and normal to it, 2 delta epsilon perpendicular, were calculated from the CD spectra of the oriented samples by the method of Chung and Holzwarth, (1975) J. Mol. Biol. 92, 449--466. It was shown that in most cases, except that of the protonated DNA, the degree of orientation was only slightly less than that for pure DNA. This demonstrated the absence of aggregation and of appreciable denaturation. In all cases the modifications of DNA give rise to a negative component 2 delta epsilon perpendicular, whose magnitude increased as the extent of modification increased. From both the CD spectra of non-oriented samples and the absorption spectra, an inference is drawn that Ag1+ and Cu1+ are attached to the same site as CH3 groups i.e., to the N7 atom of guanine. Proton transfer along the H-bond from the N1 atom of G to the N3 atom of the complementary cytosine is suggested to be a result of the modifications, although the case of H+-DNA may differ from the others. Based on the CD spectra for the anisotropic components, delta epsilon parallel and 2 delta epsilon perpendicular, it is proposed that ligand binding is accompanied by winding of the DNA helix.
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PMID:Circular dichroism anisotrophy of DNA with different modifications at N7 of guanine. 38 54

A model for the structure and function of extracellular carboxyl (acid) proteases can be established from three amino acid sequences and four crystal structures of these enzymes. The carboxyl proteases from gastric and fungal origins are very homologous in both primary and tertiary structures. The molecules consist of about 320 residues organized with a secondary structure which is primarily comprised of beta-strands and very similar tertiary structures. An apparent binding cleft, which can accommodate a substrate with about eight amino acid residues, contains near its midpoint the active center residues Asp-215, Asp-32, and Ser-35. These three residues are hydrogen bonded to each other. An intracellular carboxyl protease, cathepsin D, is very homologous to the extracellular enzymes in N-terminal amino acid sequence and primary structure location of active center residues. The tertiary structure of cathepsin D is probably similar, as well. However, cathepsin D contains a unique hydrophobic "tail" made up of about 100 residues added on the C-terminal side. Cathepsin D precursor is over 100,000 daltons in molecular weights, as contrasted to the gastric carboxyl protease zymogens, which are about 40,000 daltons. Carboxyl proteases contain two lobes symmetrical in peptide chain conformations. Each of the lobes also consists of two homologous structural units. These structural characteristics suggest that the original gene was coded for only about eighty amino acid residues and that gene duplication and fusion has taken place twice to produce a single chain carboxyl protease with four basic structural units in two symmetrical lobes. The formation of the zymogens and the cathepsin D "tail" must have resulted from various gene fusions. Partial sequence comparisons also suggest that cathepsin D may be an evolutionary ancestral chain for gastric carboxyl proteases.
Mol Cell Biochem 1979 Jul 31
PMID:Evolution in the structure and function of carboxyl proteases. 38 85

The modified Tanford-Kirkwood theory of Shire et al. [Shire, S. J., Hanania, G.I.H., & Gurd, F.R.N. (1974) Biochemistry 13, 2967] for electrostatic interactions was applied to the hydrogen ion equilibria of human deoxyhemoglobin and oxyhemoglobin. Atomic coordinates for oxyhemoglobin were generated by the application of the appropriate rigid rotation function to alpha and beta chains of the deoxyhemoglobin structure [Fermi, G. (1975) J. Mol. Biol. 97, 237]. The model employs two sets of parameters derived from the crystalline protein structures, the atomic coordinates of charged amino acid residues and static solvent accessibility factors to reflect their individual degrees of exposure to solvent. Theoretical titration curves based on a consistent set of pKint values compared closely with experimental potentiometric curves. Theoretical pK values at half-titration for individual protein sites corresponded to available observed values for both quaternary states. The results bring out the cumulative effects of numerous electrostatic interactions in the tetrameric structures and the major effects of the quaternary transition that result from changes in static solvent accessibility of certain ionizable groups.
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PMID:Electrostatic effects in hemoglobin: hydrogen ion equilibria in human deoxy- and oxyhemoglobin A. 43 57

Earlier we have shown that DNA forms stoichiometric complexes with bis-(2-guanidoethyl)-disulfide (GED), the helix being transformed from the B-like structure into the C-like one. The present work demonstrates that the DNA helix in the saturated complex does not change its conformation within a broad range of conditions: 0 less than [NaCl] less than 5.10(-2) M; 0% less than [methanol] less than 60% (v/v); 5 degrees less than temperature less than 50 degrees. Free DNA undergoes a non-cooperative winding within the B-family under all these influences. Increase in NaCl concentration beyond 5.10(-2) M results in abrupt cooperative unwinding from the C-like form to the B-like one, apparently due to GED dissociation. The obtained data are in accord with the idea that the conformational transition of DNA within the B-family is induced by change of phosphates interaction with the hydrated cations of alcaline metals; formation of strong hydrogen bonds of the phosphates with GED makes the DNA helix non-sensitive to variations of the environment.
Mol Biol (Mosk)
PMID:[Bis-(2-guanidoethyl)-disulfide, when complexed with DNA, prevents its winding within the B-family]. 46 Jan 89

The electronic-conformational interactions (ECI) of enzyme-substrate complexes are treated with the help of the method of intermolecular orbitals. The applicability of this approach is shown concerning some problems, related to ECI. The activation of N2 in the active site of nitrogenase, the proton transfer in the system, containing hydrogen bonds, and the modelling of the initial state of the reaction of lysozyme with oligosaccharides were examined.
Mol Biol (Mosk)
PMID:[Electronic-conformational interactions of molecular-biological systems. II. Study of the enzyme-substrate complex with the help of qualitative methods of quantum chemistry]. 46 Jan 99

The intermolecular interaction of bacteriochlorophyll c and its pheophytin was studied in nonpolar solvents and solid films with the aid of absorption and infra-red (in the region of 1800--1600 and 3800--3000 cm-1) spectra. The influence of water removing and its addition on these spectra has been investigated. Besides the effect of pyridine treatment and pigment concentration were examined. The self-assemblage of all types of bacteriochlorophyll c aggregated forms absorbing in the range 680--745 nm is due to the formation of intermolecular bonds in which keto groups of cyclopentanone rings take part. Keto groups form coordinate bonds with the central magnesium atom (keto-C = O...Mg). Hydroxyl groups interact coordinately with magnesium and simultaneously form hydrogen bonds with pyrrol nitrogen. In contrast to chlorophyll a and bacteriochlorophyll a, water molecules in the case of bacteriochlorophyll c do not participate in the intermolecular bond formation in the course of long-wave aggregated forms production. The thermostability of bacteriochlorophyll c aggregates and their rather high stability to desaggregating agents is related to the mentioned peculiarities of their structure. Bacteriopheophytin c in any state (solution or solid film) is not capable to form intermolecular bonds by its carbonyl groups and long-wave aggregates. The specific features of the assemblage of bacteriochlorophyll c aggregates modelling antenna of the green photosynthetic bacteria are discussed.
Mol Biol (Mosk)
PMID:[Molecular mechanism of self-assembly of aggregated bacteriochlorophyll c]. 46 Feb 4

The method of hydrogen exchange is used to determine the mobility of acid-soluble collagen molecules from animals with different physiological temperature in terms of equilibrium constants of the formation of micro-unfolding or fluctuating defects of the structure. It has been shown that mobility of the collagen structure correlates with the physiological temperature of the animal from whose tissue collagen was isolated and is mainly determined by the amino acid content of the collagen. It has been shown also that at physiological temperatures characteristic for a particular species the level of collagen mobility is of the same order despite their different thermostability. The conclusion has been drawn that the level of mobility is the main criterion at the natural selection of the amino acid composition of collagens in different animals.
Mol Biol (Mosk)
PMID:[Mobility of collagen structure and temperature adaptation of animals]. 46 Feb 8

Conformational properties of the neurotoxin apamine were investigated starting from the known amino acid sequence. Nonvalent and electrostatic interactions, hydrogen bonding and torsional energies were computed by variation of all backbone and side chain dihedral angles. In a search for the spatial structure of the molecule, di-, tri-, tetra- etc. fragments were subsequently analyzed. As the result, the apriori calculations of the 15-residue apamine fragment revealed strong energy differentiations of forms. The lowest energy conformation has a folded backbone, with an orientation of Cys-1--Cys-11 and Cys-3--Cys-15 side chain pairs favoring the formation of disulfide bridges.
Mol Biol (Mosk)
PMID:[Semiempirical calculations of the structure of apamine]. 47 Sep 48

A laboratory study of the interaction of H2O frost with samples of the minerals olivine (Mg,Fe)2SiO4 and pyroxene (Mg,Fe)SiO3 at -11 degrees C to -22 degrees C revealed that an acidic oxidant was produced. Exposure of the frost-treated minerals to liquie H2O produced a sudden drop in pH and resulted in the production of copious O2(g) (as much as approximately 10(20) molecules g-1). Exposure of frost-treated samples to 5 ml of 0.1M HCOONa solution resulted in the rapid oxidation of up to 43% of the formate to CO2(g). These reactions were qualitatively similar to the chemical activity observed during the active cycles of the Viking lander Gas Exchange and Labeled Release Biology experiments. Attempts to identify the oxidant by chemical indicators were inconclusive, but they tentatively suggested that chemisorbed hydrogen peroxide may have formed. The formation of chemisorbed peroxide could be explained as a byproduct of the chemical reduction of the mineral. The following model was proposed. H+ was incorporated into the mineral from surface frost. This would have left behind a residual of excess OH-(ads) (relative to surface H+). Electrons were then stripped from the surface OH-(ads) (due to the large repulsive potential between neighboring OH-(ads)) and incorporated into the crystal to restore charge balance and produce a chemical reduction of the mineral. The resultant surface hydroxyl radicals could then have combined to form the more stable chemisorbed hydrogen peroxide species. While the chemisorbed peroxide should be relatively stable at low temperatures, it should tend to decay to O(ads)+ H2O(g) at higher temperatures with an activation energy of greater than or approximately 34 kcal mole-1. This is consistent with the long-term storage and sterilization behavior of the Viking soil oxidants. It is possible that as little as 0.1--1% frost-weathered material in the martian soil could have produced the unusual chemical activity that occurred during the Viking Gas Exchange and Labeled Release experiments.
J Mol Evol 1979 Dec
PMID:Frost-weathering on Mars: experimental evidence for peroxide formation. 52 48


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