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Biomedical subjects

W Saenger

Publications and source records attributed to W Saenger.

At least 199 records · Page 11Linked to original sources
PubMed1980

Three-dimensional structure of the "long" neurotoxin from cobra venom.

The three-dimensional structure of alpha-cobra-toxin, the "long" neurotoxin from the venom of Naja naja siamensis, has been determined at 2.8-A resolution. Crystals grown as hexagonal needles have space group P6522 with unit cell parameters a = b = 74.59 A, c = 42.89 A; one molecule per asymmetric unit. Phases were determined with a single isomorphous derivative with HgI2 by using the anomalous scattering of the single-site HgI2 molecule to resolve the phase ambiguity. The polypeptide chain folds into three major loops and one tail emerging from a globular head. The protruding long central loop (residues 21-40) is flanked on either side by two shorter loops (residues 4-13 and 44-55); the tail piece (residues 63-71) hangs behind this loop. The molecular conformation is determined by four disulfides in the head and one at the tip of the long loop, by a triple-stranded beta-pleated sheet involving this loop, and by hydrophobic interactions stabilizing the other two loops. The structure of alpha-cobratoxin is compared to that described for the "short" erabutoxin b which shows similar arrangement of structurally and functionally invariant groups.

Animals↗
PubMed1980

On the structure of crystalline ribulosebisphosphate carboxylase from Alcaligenes eutrophus.

Ribulosebisphosphate carboxylase from the hydrogen bacterium Alcaligenes eutrophus having a molecular weight of 534000 and consisting of eight large and eight small subunits has been crystallized by microdialysis using inorganic as well as organic precipitating agents. Crystals have tetragonal space group P42212, a = b = 11.27 nm, c = 20.14 nm, and contain one quarter molecule per asymmetric unit. X-rays are diffracted to 0.35-nm resolution on still photographs. Light optical diffractions of electron micrographs of thin sectioned crystals displayed patterns which could be interpreted on the basis of the unit cell determined by X-rays. Packing considerations are in accord with our earlier proposal regarding the subunit arrangement of this enzyme which differs from that reported for tobacco ribulosebisphosphate carboxylase.

Alcaligenes↗
PubMed1980

Crystallization of a complex between ribonuclease T1 and 2'-guanylic acid.

Ribonuclease T1 was crystallized under various conditions. Form I crystals were produced by microdialysis against 53% (v/v) 2-methyl-2,4-pentanediol in 0.01 M sodium acetate, 0.05% 2'-guanylic acid (2'GMP) and 0.02% NaN3 (pH 6.2-7.2). These crystals are tetragonal, space group P41212 and contain two molecules per asymmetric unit; cell dimensions are a = b = 5.86 nm, c = 13.28 nm. Form IIa and form IIb crystals were obtained by microdialysis from a buffer of 0.01-0.05 M sodium acetate, 0.25-0.5% 2'GMP, 0.02% NaN3 and 2-5 mM calcium acetate (pH 4.0-4.4) in the presence of 50-75% (v/v) 2-methyl-2,4-pentanediol. These crystals are orthorhombic, space group P212121, and contain one molecule per asymmetric unit; cell dimensions are a = 4.66 nm, b = 5.02 nm, c = 4.04 nm (form I) and alpha = 4.44 nm, b = 5.00 nm, c = 4.03 nm (form II). Using high-performance liquid chromatography, it could be shown for all crystal forms that 2'-GMP is bound in the crystals. The molecular ratio between RNase T1 and 2'GMP was 0.9 for form II crystals and thus agreed with a 1:1 enzyme-nucleotide complex. Heavy-atom derivatives were produced with lead acetate for form IIa crystals and with uranyl acetate for from IIb crystals. Three-dimensional X-ray analysis of the RNase-T1 x 2'GMP complex is under way.

Aspergillus oryzae↗
PubMed1979

Crystal and molecular structure of adenosine 5'-O-phosphorothioate O-p-nitrophenyl ester (Sp diastereomer). Substrate stereospecificity of snake venom phosphodiesterase.

Phosphorylation of 2',3'-O-methoxymethylidene adenosine with bis(p-nitrophenyl) O,O-phosphorochloridothioate, followed by alkaline and acidic deprotection, afforded a mixture of the Rp and Sp diastereomers of adenosine 5'-O-phosphorothioate O-p-nitrophenyl ester in good yield. Only one of these diastereomers is a substrate for snake venom phosphodiesterase. The other diastereomer, remaining after complete enzymatic digestion of the substrate, was crystallized as the triethylammonium salt in the triclinic space group P1. The structure was solved from three-dimensional X-ray data and refined to an R value of 5.2%. The asymmetric cell unit contains two independent molecules with almost identical conformations. The ribose is puckered C(2')-endo, the heterocycle is in anti position and the C(5')-O(5') bond gauche, gauche. The triethylammonium cation is coordinated to the free oxygen of the phosphorothioate group and the P-S bond has double bond character. The absolute configuration of the phosphorous is Sp. This is in agreement with an earlier stereochemical study of the hydrolysis of the diastereomers of 5'-O-adenosyl 3'-O-uridyl phosphorothioate by snake venom phosphodiesterase.

Adenine Nucleotides↗
PubMed1978

Theoretical investigations on the conformation of 1,5,N(4),N(4)-tetramethylcytosine.

Theoretical investigations (Perturbative Configuration Interaction over Localized Orbitals (PCILO) and Intermediate Neglect of Differential Overlap (INDO) methods) of the conformation of tetramethylcystosine, an overcrowded molecule with planar structure, have been carried out. The physical features of rotational bending potentials of the dimethylamino group are discussed. Particularly, the controversial problem concerning the planarity of the molecule is investigated. The obtained results show that the planarity of tetramethylcytosine is an intrinsic property of the molecule. Nevertheless, because of the repulsion between the methyl groups, the planar structure of tetramethylcytosine is slightly destabilized. Further, the functional dependence of the dipole moment of tetramethylcytosine on rotation and bending of the dimethylamino group has been analyzed.

5-Methylcytosine↗
PubMed1977

X-ray study of the lithium complex of NAD.

The Li+-NAD+ complex exists as a 'dimer' of two molecules arranged head-to-tail with Li+ coordinated tetrahedrally to adenine N(7) and three pyrophosphate oxygens. Adenine is stacked intermolecularly on nicotinamide. The conformation of NAD+ is 'extended' and similar to that found in holoenzyme complexes. This is in contrast to the 'folded' structure proposed from spectroscopic studies.

Cations, Monovalent↗