ABSTRACT
The crystal structure of alanine racemase from Oenococcus oeni has been determined at 1.7â Å resolution using the single-wavelength anomalous dispersion (SAD) method and selenium-labelled protein. The protein exists as a symmetric dimer in the crystal, with both protomers contributing to the two active sites. Pyridoxal 5'-phosphate, a cofactor, is bound to each monomer and forms a Schiff base with Lys39. Structural comparison of alanine racemase from O. oeni (Alr) with homologous family members revealed similar domain organization and cofactor binding.
Subject(s)
Alanine Racemase/chemistry , Alanine Racemase/metabolism , Oenococcus/enzymology , Pyridoxal Phosphate/metabolism , Alanine Racemase/genetics , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Catalytic Domain , Crystallography, X-Ray , Models, Molecular , Protein Conformation , Protein Folding , Protein Multimerization , Pyridoxal Phosphate/chemistry , Sequence AlignmentABSTRACT
ABC transport systems have been characterized in organisms ranging from bacteria to humans. In most bacterial systems, the periplasmic component is the primary determinant of specificity of the transport complex as a whole. Here, the X-ray crystal structure of a periplasmic glucose-binding protein (GBP) from Thermotoga maritima determined at 2.4â Å resolution is reported. The molecule consists of two similar α/ß domains connected by a three-stranded hinge region. In the current structure, a ligand (ß-D-glucose) is buried between the two domains, which have adopted a closed conformation. Details of the substrate-binding sites revealed features that determine substrate specificity. In toto, ten residues from both domains form eight hydrogen bonds to the bound sugar and four aromatic residues (two from each domain) stabilize the substrate through stacking interactions.
Subject(s)
Bacterial Proteins/chemistry , Glucose/metabolism , Periplasmic Binding Proteins/chemistry , Thermotoga maritima/metabolism , Amino Acid Sequence , Bacterial Proteins/metabolism , Binding Sites , Carrier Proteins/chemistry , Carrier Proteins/metabolism , Crystallography, X-Ray , Hydrogen Bonding , Molecular Sequence Data , Periplasmic Binding Proteins/metabolism , Protein Conformation , Sequence Alignment , Substrate SpecificityABSTRACT
2-Chloro-3-(beta-nitrovinyl)quinoline (CNQ) was crystallographically studied owing to its medicinal properties and its occurrance in numerous commercial products, including pharmaceuticals, fragrances and dyes. The vinyl group is planar, and takes up an extended conformation. An hydrogen bonding of C-H...N type helps to stabilize the molecules in the unit cell.
Subject(s)
Hydrogen-Ion Concentration , Crystallography , Molecular StructureABSTRACT
4-(4'-Diethylaminophenyl)-6-(4-methoxyphenyl)-(2-pyrrolidin-1-yl)-pyridine-3-carbonitrile (DMPPC) was studied by X-ray diffraction methods due to its non-linear optical properties. The pyrrolidine and pyridine rings adopt half-chair and planar conformations, respectively. The molecules in the crystal are stabilized by C-H...O and C-H...N types of intermolecular interactions in addition to van der Waals forces.
