Functional details of the Mycobacterium tuberculosis VapBC26 toxin-antitoxin system based on a structural study: insights into unique binding and antibiotic peptides.

Toxin-antitoxin (TA) systems are essential for bacterial persistence under stressful conditions. In particular, Mycobacterium tuberculosis express VapBC TA genes that encode the stable VapC toxin and the labile VapB antitoxin. Under normal conditions, these proteins interact to form a non-toxic TA complex, but the toxin is activated by release from the antitoxin in response to unfavorable conditions.

Alba from Thermoplasma volcanium belongs to α-NAT's: An insight into the structural aspects of Tv Alba and its acetylation by Tv Ard1.

The Alba superfamily proteins have been regarded as a conserved group of proteins in archaea and eukarya, which have shown to be important in nucleic acid binding, chromatic organization and gene regulation. These proteins often belong to the N-acetyltransferase (NAT) category (N(α)-acetyltransferases or N(ε)-acetyltransferases) and undergo post-translational modifications. Here, we report the crystal structure of Alba from Thermoplasma volcanium (Tv Alba) at 2.

Identification of novel scaffolds for potential anti-Helicobacter pylori agents based on the crystal structure of H. pylori 3-deoxy-d-manno-octulosonate 8-phosphate synthase (HpKDO8PS).

The crystal structure of 3-deoxy-d-manno-octulosonate-8-phosphate synthase (KDO8PS) from Helicobacter pylori (HpKDO8PS) was determined alone and within various complexes, revealing an extra helix (HE) that is absent in the structures of KDO8PS from other organisms. In contrast to the metal coordination of the KDO8PS enzyme from Aquifex aeolicus, HpKDO8PS is specifically coordinated with Cd(2+) or Zn(2+) ions, and isothermal titration calorimetry (ITC) and differential scanning fluorimetry (DSF) revealed that Cd(2+) thermally stabilizes the protein structure more efficiently than Zn(2+). In the substrate-bound structure, water molecules play a key role in fixing residues in the proper configuration to achieve a compact structure.

β-Arm flexibility of HU from Staphylococcus aureus dictates the DNA-binding and recognition mechanism.

HU, one of the major nucleoid-associated proteins, interacts with the minor groove of DNA in a nonspecific manner to induce DNA bending or to stabilize bent DNA. In this study, crystal structures are reported for both free HU from Staphylococcus aureus Mu50 (SHU) and SHU bound to 21-mer dsDNA. The structures, in combination with electrophoretic mobility shift assays (EMSAs), isothermal titration calorimetry (ITC) measurements and molecular-dynamics (MD) simulations, elucidate the overall and residue-specific changes in SHU upon recognizing and binding to DNA.

Structure of Thermoplasma volcanium Ard1 belongs to N-acetyltransferase family member suggesting multiple ligand binding modes with acetyl coenzyme A and coenzyme A.

Acetylation and deacetylation reactions result in biologically important modifications that are involved in normal cell function and cancer development. These reactions, carried out by protein acetyltransferase enzymes, act by transferring an acetyl group from acetyl-coenzymeA (Ac-CoA) to various substrate proteins. Such protein acetylation remains poorly understood in Archaea, and has been only partially described.

Structures of inactive CRP species reveal the atomic details of the allosteric transition that discriminates cyclic nucleotide second messengers.

The prokaryotic global transcription factor CRP has been considered to be an ideal model for in-depth study of both the allostery of the protein and the differential utilization of the homologous cyclic nucleotide second messengers cAMP and cGMP. Here, atomic details from the crystal structures of two inactive CRP species, an apo form and a cGMP-bound form, in comparison with a known active conformation, the cAMP-CRP complex, provide macroscopic and microscopic insights into CRP allostery, which is coupled to specific discrimination between the two effectors. The cAMP-induced conformational transition, including dynamic fluctuations, can be driven by the fundamental folding forces that cause water-soluble globular proteins to construct an optimized hydrophobic core, including secondary-structure formation.

Crystal structure of toxin HP0892 from Helicobacter pylori with two Zn(II) at 1.8 Å resolution.

Antibiotic resistance and microorganism virulence have been consistently exhibited by bacteria and archaea, which survive in conditions of environmental stress through toxin-antitoxin (TA) systems. The HP0892-HP0893 TA system is one of the two known TA systems belonging to Helicobacter pylori. The antitoxin, HP0893, binds and inhibits the HP0892 toxin and regulates the transcription of the TA operon.

Solution structure of Rv0569, potent hypoxic signal transduction protein, from Mycobacterium tuberculosis.

The latent infection is unique characteristic of Mycobacterium tuberculosis to overcome human immune response for its survival. The M. tb develops adaptation to extreme stress conditions to increase the viability, thus easily acquires drug resistance than any other bacteria and maintains a long-term infection status without any symptoms.

Crystal structure of apo and copper bound HP0894 toxin from Helicobacter pylori 26695 and insight into mRNase activity.

The toxin-antitoxin (TA) systems widely spread among bacteria and archaea are important for antibiotic resistance and microorganism virulence. The bacterial kingdom uses TA systems to adjust the global level of gene expression and translation through RNA degradation. In Helicobacter pylori, only two TA systems are known thus far.

Overexpression, crystallization and preliminary X-ray crystallographic analysis of hypothetical protein SAV0479 from Staphylococcus aureus Mu50.

SAV0479, a hypothetical protein from the Mu50 strain of methicillin- and vancomycin-resistant Staphylococcus aureus, was selected for structure and function determination as part of a structural genomics project. Here, the cloning, overexpression, purification and crystallization of SAV0479 are reported. Crystals were obtained by the hanging-drop vapour-diffusion method and diffraction data were collected to a resolution of 2.

Structural and biochemical characterization of HP0315 from Helicobacter pylori as a VapD protein with an endoribonuclease activity.

VapD-like virulence-associated proteins have been found in many organisms, but little is known about this protein family including the 3D structure of these proteins. Recently, a relationship between the Cas2 family of ribonucleases associated with the CRISPR system of microbial immunity and VapD was suggested. Here, we show for the first time the structure of a member of the VapD family and present a relationship of VapD with Cas2 family and toxin-antitoxin (TA) systems.

The crystal structure of alanine racemase from Streptococcus pneumoniae, a target for structure-based drug design.

Background: Streptococcus pneumoniae is a globally important pathogen. The Gram-positive diplococcus is a leading cause of pneumonia, otitis media, bacteremia, and meningitis, and antibiotic resistant strains have become increasingly common over recent years. Alanine racemase is a ubiquitous enzyme among bacteria and provides the essential cell wall precursor, D-alanine.

Structure of substrate-free human insulin-degrading enzyme (IDE) and biophysical analysis of ATP-induced conformational switch of IDE.

Insulin-degrading enzyme (IDE) is a zinc metalloprotease that hydrolyzes amyloid-beta (Abeta) and insulin, which are peptides associated with Alzheimer disease (AD) and diabetes, respectively. Our previous structural analysis of substrate-bound human 113-kDa IDE reveals that the N- and C-terminal domains of IDE, IDE-N and IDE-C, make substantial contact to form an enclosed catalytic chamber to entrap its substrates. Furthermore, IDE undergoes a switch between the closed and open conformations for catalysis.

Purification and preliminary crystallization of alanine racemase from Streptococcus pneumoniae.

Background: Over the past fifteen years, antibiotic resistance in the Gram-positive opportunistic human pathogen Streptococcus pneumoniae has significantly increased. Clinical isolates from patients with community-acquired pneumonia or otitis media often display resistance to two or more antibiotics. Given the need for new therapeutics, we intend to investigate enzymes of cell wall biosynthesis as novel drug targets.

The 1.9 A crystal structure of alanine racemase from Mycobacterium tuberculosis contains a conserved entryway into the active site.

We report the crystal structure of alanine racemase from Mycobacterium tuberculosis (Alr(Mtb)) at 1.9 A resolution. In our structure, Alr(Mtb) is found to be a dimer formed by two crystallographically different monomers, each comprising 384 residues.

Crystal structure at 1.45 A resolution of alanine racemase from a pathogenic bacterium, Pseudomonas aeruginosa, contains both internal and external aldimine forms.

The structure of the catabolic alanine racemase, DadX, from the pathogenic bacterium Pseudomonas aeruginosa, reported here at 1.45 A resolution, is a dimer in which each monomer is comprised of two domains, an eight-stranded alpha/beta barrel containing the PLP cofactor and a second domain primarily composed of beta-strands. The geometry of each domain is very similar to that of Bacillus stearothermophilus alanine racemase, but the rotation between domains differs by about 15 degrees.

Characterization and crystallization of active domains of a novel luciferase from a marine dinoflagellate.

Lingulodinium polyedrum luciferase is a bioluminescent protein found in the marine dinoflagellate formerly known as Gonyaulax. It is located in organelles called scintillons that emit brief and bright flashes of light that are regulated by an endogenous circadian clock. The complete luciferase molecule has a molecular mass of 136 994 Da and contains three homologous domains, each of which is a separately active luciferase.