title: The Escherichia coli CysZ is a pH dependent sulfate transporter that can be inhibited by sulfite.
abstract: The Escherichia coli inner membrane protein CysZ mediates the sulfate uptake subsequently utilized for the synthesis of sulfur-containing compounds in cells. Here we report the purification and functional characterization of CysZ. Using Isothermal Titration Calorimetry, we have observed interactions between CysZ and its putative substrate sulfate. Additional sulfur-containing compounds from the cysteine synthesis pathway have also been analyzed for their abilities to interact with CysZ. Our results suggest that CysZ is dedicated to a specific pathway that assimilates sulfate for the synthesis of cysteine. Sulfate uptake via CysZ into E. coli whole cells and proteoliposome offers direct evidence of CysZ being able to mediate sulfate uptake. In addition, the cysteine synthesis pathway intermediate sulfite can interact directly with CysZ with higher affinity than sulfate. The sulfate transport activity is inhibited in the presence of sulfite, suggesting the existence of a feedback inhibition mechanism in which sulfite regulates sulfate uptake by CysZ. Sulfate uptake assays performed at different extracellular pH and in the presence of a proton uncoupler indicate that this uptake is driven by the proton gradient.
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala Biomedical Center, Box 596, 75124 Uppsala, Sweden.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala Biomedical Center, Box 596, 75124 Uppsala, Sweden.
authors.forename: Wangshu
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala Biomedical Center, Box 596, 75124 Uppsala, Sweden.
authors.forename: Jie
authors.initials: J
authors.lastname: Nan
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala Biomedical Center, Box 596, 75124 Uppsala, Sweden. Electronic address: jonas.almqvist@icm.uu.se.
authors.forename: Jonas
authors.initials: J
authors.lastname: Almqvist
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala Biomedical Center, Box 596, 75124 Uppsala, Sweden. Electronic address: yafei@xray.bmc.uu.se.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Huang
mesh_terms: D001692:Biological Transport; D003545:Cysteine / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism; D011522:Protons; D013431:Sulfates / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D011510:Proteolipids; D011522:Protons; D013431:Sulfates; C020485:proteoliposomes; D003545:Cysteine
keywords: CysZ; Inhibition; Membrane protein; Sulfate; Transport