In vivo recognition of the fecA3 target promoter by Helicobacter pylori NikR.

In Helicobacter pylori, the transcriptional regulator HpNikR represses transcription of the fecA3 gene by binding to two adjacent operators spanning a region of almost 80 nucleotides along the fecA3 promoter in a nickel-dependent manner. By employing hydroxyl radical footprinting, we mapped the protected nucleotides within each operator. Three short sequences rich in A and T nucleotides were identified within each operator, comprising just 24 bases for both operators, with 4 or 5 protected bases interspaced by 4 to 7 free nucleotides, with no center of symmetry.

Differential accumulation of form I RubisCO in Rhodopseudomonas palustris CGA010 under Photoheterotrophic growth conditions with reduced carbon sources.

Rhodopseudomonas palustris is unique among characterized nonsulfur purple bacteria because of its capacity for anaerobic photoheterotrophic growth using aromatic acids. Like growth with other reduced electron donors, this growth typically requires the presence of bicarbonate/CO(2) or some other added electron acceptor in the growth medium. Proteomic studies indicated that there was specific accumulation of form I ribulose 1, 5-bisphosphate carboxylase/oxygenase (RubisCO) subunit proteins (CbbL and CbbS), as well as the CbbX protein, in cells grown on benzoate without added bicarbonate; such cells used the small amounts of dissolved CO(2) in the medium to support growth.

Growth phase and metal-dependent transcriptional regulation of the fecA genes in Helicobacter pylori.

Balancing metal uptake is essential for maintaining a proper intracellular metal concentration. Here, we report the transcriptional control exerted by the two metal-responsive regulators of Helicobacter pylori, Fur (iron-dependent ferric uptake regulator) and NikR (nickel-responsive regulator), on the three copies of the fecA genes present in this species. By monitoring the patterns of transcription throughout growth and in response to nickel, iron, and a metal chelator, we found that the expression of the three fecA genes is temporally regulated, responds to metals in different ways, and is selectively controlled by either one of the two regulators.

High-affinity Ni2+ binding selectively promotes binding of Helicobacter pylori NikR to its target urease promoter.

NikR is a prokaryotic transcription factor that regulates the expression of Ni2+ enzymes and other proteins involved in Ni2+ trafficking. In the human pathogen Helicobacter pylori, NikR controls transcription of the Ni2+ enzyme urease, which allows survival of the bacterium in the acidic gastric niche. The in vitro affinity of NikR from H.

Phosphotransfer reactions of the CbbRRS three-protein two- component system from Rhodopseudomonas palustris CGA010 appear to be controlled by an internal molecular switch on the sensor kinase.

The CbbRRS system is an atypical three-protein two-component system that modulates the expression of the cbb(I) CO(2) fixation operon of Rhodopseudomonas palustris, possibly in response to a redox signal. It consists of a membrane-bound hybrid sensor kinase, CbbSR, with a transmitter and receiver domain, and two response regulator proteins, CbbRR1 and CbbRR2. No detectable helix-turn-helix DNA binding domain is associated with either response regulator, but an HPt domain and a second receiver domain are predicted at the C-terminal region of CbbRR1 and CbbRR2, respectively.

A novel three-protein two-component system provides a regulatory twist on an established circuit to modulate expression of the cbbI region of Rhodopseudomonas palustris CGA010.

A novel two-component system has been identified in the cbb(I) region of the nonsulfur purple photosynthetic bacterium Rhodopseudomonas palustris. Genes encoding this system, here designated cbbRRS, are juxtaposed between the divergently transcribed transcription activator gene, cbbR, and the form I ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) genes, cbbLS. The three genes of the cbbRRS system represent a variation of the well-known two-component signal transduction systems, as there are a transmembrane hybrid sensor kinase and two response regulators, with no apparent DNA binding domain associated with any of the three proteins encoded by these genes.

Tactic responses to oxygen in the phototrophic bacterium Rhodobacter sphaeroides WS8N.

The temporal and spatial behavior of a number of mutants of the photosynthetic, facultative anaerobe Rhodobacter sphaeroides to both step changes and to gradients of oxygen was analyzed. Wild-type cells, grown under a range of conditions, showed microaerophilic behavior, accumulating in a 1.3-mm band about 1.