Mechanism of Proton Gating of a Urea Channel

Weeks, David L.; Gushansky, Gene; Scott, David; Sachs, George

doi:10.1074/jbc.m312680200

Cited by 29 publications

(28 citation statements)

References 27 publications

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“…These data provide further evidence for exposure of the periplasm in vivo to a pH that activates HP0165 at a pH Ϸ5.9, the pH for half maximal activation of UreI and close to the pK a of histidine (50,51). This is close to the calculated periplasmic pH found in vitro when the pH out was pH 3.0 (9).…”

Section: Discussionsupporting

confidence: 62%

Gene expression in vivo shows that Helicobacter pylori colonizes an acidic niche on the gastric surface

Scott

Marcus

Wen

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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105

127

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Helicobacter pylori is a gastric-dwelling pathogen responsible, with acid secretion, for peptic ulcer and a 20-fold increase in the risk of gastric cancer. Several transcriptomes have been described after short-term exposure to acidity in vitro, but there are no data identifying the effects of chronic gastric exposure on bacterial gene expression. Comparison of the in vivo to the in vitro transcriptome at pH 7.4 identified several groups of genes of known function that increased expression >2-fold, and three of these respond both to acidity in vitro and to gastric infection. Almost all known acid acclimation genes are highly up-regulated. These include ureA, ureB, and rocF and the pH-gated urea channel, ureI. There is also up-regulation of two groups of motility and chemotaxis genes and for pathogenicity island genes, especially cagA, a predictor for pathogenicity. Most of these genes interact with HP0166, the response element of the pH-sensing two-component histidine kinase, HP0165/HP0166, ArsRS. Based on the pH profile of survival of ureI deletion mutants in vitro and their inability to survive in gastric acidity, the habitat of the organism at the gastric surface is acidic with a pH < 4.0. Hence, the pH of the habitat of H. pylori on the surface of the stomach largely determines the regulation of these specific groups of genes.acid acclimation ͉ gastric pH ͉ global transcriptome ͉ microarray

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Section: Discussionsupporting

confidence: 62%

Gene expression in vivo shows that Helicobacter pylori colonizes an acidic niche on the gastric surface

Scott

Marcus

Wen

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

105

127

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“…This indicates that in H. hepaticus there is probably no promoter directly upstream of the ureI gene, thus limiting the possibilities for transcriptional and post-transcriptional regulation (Akada et al, 2000;van Vliet et al, 2001). Furthermore, the overall amino acid sequence of UreI in both species is well conserved, but several amino acid residues which were shown to be required for acid activation of the H. pylori UreI urea channel are absent in the H. hepaticus UreI protein (Weeks et al, 2004). This is consistent with the extragastric lifestyle of H. hepaticus and its inability to grow or survive at (Figs 1 and S1).…”

Section: Discussionmentioning

confidence: 99%

Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

et al. 2005

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Helicobacter hepaticus is a pathogen of rodents, which causes diverse enteric and hepatic inflammatory diseases and malignancies. The urease enzyme is an important colonization factor of gastric Helicobacter species like Helicobacter pylori, but little is known about the role and regulation of urease in enterohepatic Helicobacter species. Here it is reported that urease activity of H. hepaticus does not contribute to acid resistance, and that it is nickel-responsive at the post-translational level. H. hepaticus strain ATCC 51449 did not grow or survive at pH 3?0, and supplementation with urea or NiCl 2 did not abrogate this acid sensitivity. Furthermore, urease enzyme activity of H. hepaticus was acid-independent, which contrasts with the acid-induced urease system of H. pylori. Nickel supplementation of Brucella medium resulted in a tenfold increase in urease activity in both H. hepaticus and H. pylori, but the maximum level of urease activity in H. hepaticus was still three-to fivefold lower when compared to H. pylori in the same conditions. The increase in urease activity of H. hepaticus was not associated with elevation of urease mRNA or protein levels. Inhibition of protein synthesis by chloramphenicol did not affect nickel-responsive induction of urease activity in H. hepaticus, and confirmed that nickel induction occurs at the post-translational level, probably by activation of preformed apo-enzyme. In conclusion, both the role of the urease enzyme and the regulation of urease activity differ between the enterohepatic pathogen H. hepaticus and the gastric pathogen H. pylori.

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“…Histidine-Exofacial His protonation controls the pHdependent activity of many ion channel polypeptides (27)(28)(29).…”

Section: Role Of Charged and Titratable Amino Acid Residues In Ae2 Rementioning

confidence: 99%

Acute pH-dependent Regulation of AE2-mediated Anion Exchange Involves Discrete Local Surfaces of the NH2-terminal Cytoplasmic Domain

Stewart

Kerr

Chernova

et al. 2004

Journal of Biological Chemistry

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We have previously defined in the NH 2 -terminal cytoplasmic domain of the mouse AE2/SLC4A2 anion exchanger a critical role for the highly conserved amino acids (aa) 336 -347 in determining wild-type pH sensitivity of anion transport. We have now engineered hexaAla ((A) 6 ) and individual amino acid substitutions to investigate the importance to pH-dependent regulation of AE2 activity of the larger surrounding region of aa 312-578. 4,4 -Diisothiocyanostilbene-2,2 -disulfonic acid (DIDS)-sensitive 36 Cl ؊ efflux from AE2-expressing Xenopus oocytes was monitored during changes in pH i or pH o in HEPES-buffered and in 5% CO 2 /HCO 3 ؊ -buffered conditions. Wild-type AE2-mediated 36 Cl ؊ efflux was profoundly inhibited at low pH o , with a pH o(50) value ‫؍‬ 6.75 ؎ 0.05 and was stimulated up to 10-fold by intracellular alkalinization. Individual mutation of several amino acid residues at non-contiguous sites preceding or following the conserved sequence aa 336 -347 attenuated pH i and/or pH o sensitivity of 36 Cl ؊ efflux. The largest attenuation of pH sensitivity occurred with the AE2 mutant (A) 6 357-362. This effect was phenocopied by AE2 H360E, suggesting a crucial role for His 360 . Homology modeling of the three-dimensional structure of the AE2 NH 2 -terminal cytoplasmic domain (based on the structure of the corresponding region of human AE1) predicts that those residues shown by mutagenesis to be functionally important define at least one localized surface region necessary for regulation of AE2 activity by pH.The anion exchangers AE1, AE2, and AE3 are polypeptide products of the SLC4 bicarbonate transporter gene superfamily that mediate Na ϩ -independent Cl Ϫ /HCO 3 Ϫ exchange. Anion exchangers contribute to the regulation of intracellular pH (pH i ), cell volume, tonicity, and intracellular Cl (Cl Ϫ ) in metazoan cells (1-5). The AE polypeptides share a highly conserved hydrophobic, polytopic, transmembrane domain of Ͼ500 amino acids (aa), 1 with a short COOH-terminal cytoplasmic tail capable of binding carbonic anhydrase II (6, 7). This transmembrane domain is preceded by a less extensively conserved hydrophilic NH 2 -terminal cytoplasmic domain of 400 -700 aa (3). The polytopic transmembrane domain can mediate anion exchange in the absence of nearly the entire NH 2 -terminal cytoplasmic domain (8, 9). Whereas the NH 2 -terminal cytoplasmic domain of erythroid AE1 is important for its binding to multiple cytoskeletal proteins, glycolytic enzymes, and hemoglobin (10), functions of the cytoplasmic NH 2 -terminal domains of AE2 and AE3 remain less extensively investigated.The polypeptide products of the various SLC4 AE anion exchanger genes differ in their acute regulation by pH. Native AE1-mediated Cl Ϫ /HCO 3 Ϫ exchange in erythrocytes (11) and heterologous AE1-mediated Cl Ϫ /Cl Ϫ exchange in Xenopus oocytes (12, 13) both display a broad pH versus activity profile, consistent with the primary role of erythroid AE1 in facilitating CO 2 /HCO 3 Ϫ exchange between the respiring tissues and lungs (14). In contras...

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Mechanism of Proton Gating of a Urea Channel

Cited by 29 publications

References 27 publications

Gene expression in vivo shows that Helicobacter pylori colonizes an acidic niche on the gastric surface

Gene expression in vivo shows that Helicobacter pylori colonizes an acidic niche on the gastric surface

Differential regulation of urease activity in Helicobacter hepaticus and Helicobacter pylori

Acute pH-dependent Regulation of AE2-mediated Anion Exchange Involves Discrete Local Surfaces of the NH2-terminal Cytoplasmic Domain

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