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At least 343 records · Page 19Linked to original sources
PubMed1979

Structural differences between apo- and holoenzyme of horse liver alcohol dehydrogenase.

The three-dimensional structure of a ternary complex of horse liver alcohol dehydrogenase with reduced nicotinamide adenine dinucleotide and the inhibitor dimethyl sulfoxide has been determined to 4.5 A resolution independently of the apoenzyme structure. The electron density maps of both structures have been compared. The two coenzyme binding domains which form the center of the dimer molecular have retained their conformation and orientation within the molecule whereas the catalytic domains rotate and narrow the cleft between the domains. The active site becomes shielded from the solution by a combination of this rotation, local movements of a loop from residues 53 to 57 and coenzyme and substrate binding. Both subunits bind coenzyme and inhibitor to the same extent. The nicotinamide ring of the coenzyme is positioned close to the active zinc atom and the inhibitor is bound to this zinc atom. The difference between the two crystallographically independent subunits is small. The proposed mechanisms of action for the enzyme based on the apoenzyme structure are confirmed by the present investigation.

Alcohol Oxidoreductases↗
PubMed1979

Determination of cooperative interaction between clusters in Clostridium pasteurianum 2 (4Fe-4S) ferredoxin.

The effect of reducing one 4Fe-4S cluster in Clostridium pasteurianum 2 (4Fe-4S) ferredoxin on the reduction potential of the unreduced cluster has been investigated. While such an effect is suggested by both the x-ray structure of Peptococcus aerogenes 2 (4F-4S) ferredoxin and the polypeptide conformational change on reduction present in clostridial-type 2 (4Fe-4S) ferredoxins, present studies indicate that cluster-cluster cooperative interaction is not strong enough to be of functional importance in these proteins.

Clostridium↗
PubMed1977

[Diffuse x-ray wide-angle scattering of polyglutamic acid in solution].

The diffuse wide angle x-ray scattering (WAXS) of polyglutamic acid (PGA) in solution was studied using an x-ray diffractometer with small aperture of the primary beam. The scattering curve was recorded at an angular interval from (article: see text). The experimental scattering intensity of PGA with alpha-helical CD spectrum showed a maximum at 14.4 nm-1. Unordered PGA in solution yielded no maximum at this scattering angle. The studies have proved that the scattering theory can be applied to globular proteins in solution as well as to chain molecules in solution in this angular interval. The differences between the calculated scattering curves and the experimental curves indicate minor movements of the side chains of PGA in solutions and slight structuring of the solvent at the surface of the polypeptide chain.

Glutamates↗
PubMed1978

Crystallographic studies on D-amino acid oxidase.

D-amino acid oxidase, a flavoprotein from hog kidneys, has been crystalized in two different forms. Orthorhombic prisms have been obtained from the enzyme.benzoate complex at pH 8.3; the space group is C2221 and the cell dimensions are a = 325A, b = 138.8 A, c = 200 A. At lower pH values, the enzyme crystallizes in trigonal prisms with a = b = 116.0 A, c = 399 A, space group P3112 or its enantiomorph. The two crystal forms have been obtained at 28 degrees C while at 4 degrees C only weak evidence of crystallization has been detected. In both crystalline modifications, the protein is highly associated.

D-Amino-Acid Oxidase↗
PubMedDate not supplied

[DNA complexes with lysozyme].

Sedimentation method has been used to study hen egg-white lysozyme binding to glucosylated (from T2 phage) and non-glucosylated (from calf thymus) DNA under conditions similar to physiological ones (pH 7,3--7,4, ionic strength 0.07--0.24). The results indicate that lysozyme binds cooperatively to both DNA's. Binding parameters have been obtained by applying the theory of one-dimensional adsorption of small molecules on a linear homopolymer. X-ray patterns of complexes with different protein content have been obtained.

Animals↗
PubMed1976

X-ray and functional studies of hemoglobins Nancy and Cochin-Port-Royal.

The mutations in hemoglobin Nancy beta145(HC2) Tyr leads to Asp and hemoglobin Cochin-Portal-Royal beta146(HC3) His leads to Arg involve residues which are thought to be essential for the full expression of allosteric action in hemoglobin. Relative to the structure of deoxyhemoglobin A, our x-ray study of deoxyhemoglobin Nancy shows severe disordering of the beta chain COOH-terminal tetrapeptide and a possible movement of the beta heme iron atom toward the plane of the porphyrin ring. These structural perturbations result in a high oxygen affinity, reduced Bohr effect, and lack of cooperatively in hemoglobin Nancy. In the presence of inositol hexaphosphate (IHP), the Hill constant for hemoglobin Nancy increases from 1.1 to 2.0. But relative to its action on hemoglobin A, IHP is much less effective in reducing the oxygen affinity and in increasing the Bohr effect of hemoglobin Nancy. This indicates that IHP does not influence the R in equilibrium T equilibrium as much in hemoglobin Nancy as in hemoglobin A, and this probably is due to the disordering of His 143beta which is known to be part of the IHP binding site. IHP is also known to produce large changes in the absorption spectrum of methemoglobin A, but we find that it has no effect on the spectrum of methemoglobin Nancy. In contrast to the large structural changes in deoxyhemoglobin Nancy, the structure of deoxyhemoglobin Cochin-Port-Royal differs from deoxyhemoglobin A only in the position of the side chain of residue 146beta. The intrasubunit salt bridge between His 146beta and Asp 94beta in deoxyhemoglobin A is lost in deoxyhemoglobin Cochin-Portal-Royal with the guanidinium ion of Arg 146beta floating freely in solution. This small difference in structure results in a reduced Bohr effect, but does not cause a change in the Hill coefficient, the response to 2,3-diphosphoglycerate, or the oxygen affinity at physiological pH.

Allosteric Site↗
PubMedDate not supplied

[Myelin].

The lipid and protein composition and the metabolic turnover of myelin in the C.N.S., are briefly reported. For a better understanding, it seemed useful to introduce some historical data on the discovery of myelin and to give a morphological description at structural and ultrastructural level.

Animals↗