The Potassium Binding Protein Kbp Is a Cytoplasmic Potassium Sensor.
Escherichia coli possesses a number of specific K(+) influx and efflux systems that maintain an appropriate intracellular K(+) concentration. Although regulatory mechanisms have been identified for a number of these transport systems, the exact mechanism through which K(+) concentration is sensed in the cell remains unknown. In this work we show that Kbp (K(+) binding protein, formerly YgaU), a soluble 16-kDa cytoplasmic protein from Escherichia coli, is a highly specific K(+) binding protein and is required for normal growth in the presence of high levels of external K(+). Kbp binds a single potassium ion with high specificity over Na(+) and other metal ions found in biological systems, although, in common with K(+) transporters, it also binds Rb(+) and Cs(+). Dissection of the K(+) binding determinants of Kbp suggests a mechanism through which Kbp is able to sense changes in K(+) concentration over the relevant range of intracellular K(+) concentrations.
Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Khuram U
KU
Ashraf
Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Inokentijs
I
Josts
Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Khedidja
K
Mosbahi
Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Sharon M
SM
Kelly
School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Olwyn
O
Byron
Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK. Electronic address: brian.smith@glasgow.ac.uk.
Brian O
BO
Smith
Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK. Electronic address: daniel.walker@glasgow.ac.uk.
Daniel
D
Walker
D001665:Binding Sites; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D011188:Potassium / Q000378:metabolism*; D011485:Protein Binding; D012964:Sodium / Q000378:metabolism
D029968:Escherichia coli Proteins; C000595833:YgaU protein, E coli; D012964:Sodium; D011188:Potassium