The potassium binding protein Kbp is a cytoplasmic potassium sensor

Ashraf, Khuram U. and Josts, Inokentijs and Mosbahi, Khedidja and Kelly, Sharon M. and Byron, Olwyn and Smith, Brian O. and Walker, Daniel (2016) The potassium binding protein Kbp is a cytoplasmic potassium sensor. Structure, 24 (5). pp. 741-749. ISSN 0969-2126 (https://doi.org/10.1016/j.str.2016.03.017)

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Abstract

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.

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