Disruptions of Genes Encoding Ribose-5-Phosphate Isomerases in Increases Sensitivity of Bacteria to Antibiotics.

In cells, the main enzymes involved in pentose interconversion are ribose-5-phosphate isomerases RpiA and RpiB and ribulose-5-phosphate epimerase Rpe. The inactivation of limits ribose-5-phosphate (R5P) synthesis via the oxidative branch of the pentose phosphate pathway (PPP) and unexpectedly results in antibiotic supersensitivity. This type of metabolism is accompanied by significant changes in the level of reducing equivalents of NADPH and glutathione, as well as a sharp drop in the ATP pool.

CydDC functions as a cytoplasmic cystine reductase to sensitize to oxidative stress and aminoglycosides.

l-cysteine is the source of all bacterial sulfurous biomolecules. However, the cytoplasmic level of l-cysteine must be tightly regulated due to its propensity to reduce iron and drive damaging Fenton chemistry. It has been proposed that in the component of cytochrome -I terminal oxidase, the CydDC complex, shuttles excessive l-cysteine from the cytoplasm to the periplasm, thereby maintaining redox homeostasis.

Mechanism of HS-mediated protection against oxidative stress in .

Endogenous hydrogen sulfide (HS) renders bacteria highly resistant to oxidative stress, but its mechanism remains poorly understood. Here, we report that 3-mercaptopyruvate sulfurtransferase (3MST) is the major source of endogenous HS in Cellular resistance to HO strongly depends on the activity of , a gene that encodes 3MST. Deletion of the ferric uptake regulator (Fur) renders ∆ cells hypersensitive to HO Conversely, induction of chromosomal from a strong pLtetO-1 promoter (P -) renders ∆ cells fully resistant to HO Furthermore, the endogenous level of HS is reduced in ∆ or ∆ ∆ cells but restored after the addition of an iron chelator dipyridyl.

Crystallization and preliminary X-ray study of Vibrio cholerae uridine phosphorylase in complex with 6-methyluracil.

Uridine phosphorylase catalyzes the phosphorolysis of ribonucleosides, with the nitrogenous base and ribose 1-phosphate as products. Additionally, it catalyzes the reverse reaction of the synthesis of ribonucleosides from ribose 1-phosphate and a nitrogenous base. However, the enzyme does not catalyze the synthesis of nucleosides when the substrate is a nitrogenous base substituted at the 6-position, such as 6-methyluracil (6-MU).

Expression, purification, crystallization and preliminary X-ray structure analysis of Vibrio cholerae uridine phosphorylase in complex with thymidine.

A high-resolution structure of the complex of Vibrio cholerae uridine phosphorylase (VchUPh) with its physiological ligand thymidine is important in order to determine the mechanism of the substrate specificity of the enzyme and for the rational design of pharmacological modulators. Here, the expression and purification of VchUPh and the crystallization of its complex with thymidine are reported. Conditions for crystallization were determined with an automated Cartesian Dispensing System using The Classics, MbClass and MbClass II Suites crystallization kits.