Showing papers in "Acta Crystallographica in 1999"

The high-resolution structure of DNA-binding protein HU from Bacillus stearothermophilus.

Abstract: Protein HU is a ubiquitous prokaryotic protein which controls the architecture of genomic DNA. It binds DNA non-specifically and promotes the bending and supercoiling of the double helical structure. HU is involved in many DNA-associated cellular processes, including replication, transcription and the packaging of DNA into chromosome-like structures. Originally determined at medium resolution, the crystal structure of HU has now been refined at 2.0 A resolution. The high-resolution structure shows that the dimeric molecule is essentially a compact platform for two flexible and basic arms which wrap around the DNA molecule. To maximize the protein's stability, non-secondary structural regions are reduced to a minimum, there is an extensive aromatic hydrophobic core and several salt bridges and hydrogen-bonded water molecules knit together crucial regions. Based on the original medium-resolution structure of HU, several proposals were made concerning the structural basis of HU's ability to bind, bend and supercoil DNA. Each of these proposals is fully supported by the high-resolution structure. Most notably, the surfaces of the molecule which appear to mediate protein-DNA and protein-protein interactions have the ideal shapes and physicochemical properties to perform these functions.

(S)-2-Amino-3-methyl-1-butanol (2S,3S)-hydrogen tartrate monohydrate

Abstract: In the title compound, C 5 H 14 NO + .C 4 H 5 O 6 - .H 2 O, the hydrogen-bond system created by the chains of head-to-tail linked hydrogen tartrate ions and water molecules forms a V-shaped layer that is effective in discriminating between the two enantiomers of protonated 2-amino-3-methyl-1-butanol. The cation adopts a conformation that isolates its hydrophilic and hydrophobic parts, which is common for other cations containing the same N-C-C-O fragment.

Preliminary crystallographic studies of a protease resistant botulinum neurotoxin associated protein Hn-33

Abstract: Botulinum neurotoxin (BoNT) is one of the most potent toxins known. BoNT is also a food poison, which means that the toxin must survive the protease action and acidity of the gut. A group of neurotoxin-associated proteins which are only beginning to be identified and characterized are believed to be responsible for this protection. Hn-33 is a 33 kDa polypeptide which is a major component of the type A botulinum neurotoxin complex. Crystals of Hn-33 have been grown by vapour-diffusion techniques. They belong to a primitive orthorhombic space group and diffract to a resolution of 2. 6 A, with unit-cell parameters a = 130.3, b = 122.2, c = 37.2 A.

Molecular Co-crystals of 2-Aminothiazole Derivatives

Abstract: A series of molecular adducts of 2-aminothiazole derivatives - 2-aminothiazole, 2-amino-2-thiazoline and 2-aminobenzothiazole with the carboxylic-acid-substituted heterocyclics indole-2-carboxylic acid, N-methylpyrrole-2-carboxylic acid and thiophene-2-carboxylic acid - have been prepared and characterized using X-ray powder diffraction and in five cases by single-crystal X-ray diffraction methods. These five compounds are the adducts of 2-amino-2-thiazolium with indole-2-carboxylate [(C3H7N2S)+(C9H6NO2)-], and N-methylpyrrole-2-carboxylate [(C3H7N2S)+-(C6H6NO2)-], 2-aminobenzothiazolium with indole-2-carboxylate [(C7H7N2S)+(C9H6NO2)-], N-methylpyrrole-2-carboxylate [(C7H7N2S)+(C6H6NO2)-] and thiophene-2-carboxylate [(C7H7N2S)+(C5H3O2S)-]. All complexes involve proton transfer, as indicated by IR spectroscopy, while the five crystal structures display similar hydrogen-bonding patterns with the dominant interaction being an graph set dimer association between carboxylate groups and the amine/heterocyclic nitrogen sites. Futhermore, in each case a subsiduary interaction between an amino proton and a carboxylate oxygen completes a linear hydrogen-bonded chain. In addition to this, the indole-2-carboxylate molecules in the adduct structure with 2-amino-2-thiazolium form associated dimers which add to the hydrogen-bonding network.