The Potassium Binding Protein Kbp Is a Cytoplasmic Potassium Sensor

• Published in: Structure (London) 2016-05, Vol.24 (5), p.741-749
• Main Authors: Ashraf, Khuram U., Josts, Inokentijs, Mosbahi, Khedidja, Kelly, Sharon M., Byron, Olwyn, Smith, Brian O., Walker, Daniel
• Format: Article
• Language: English
• Subjects: Binding Sites; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - metabolism; Molecular Docking Simulation; Molecular Dynamics Simulation; Potassium - metabolism; Protein Binding; Sodium - metabolism
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2016.03.017

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. [Display omitted] •E. coli Kbp is a highly specific cytoplasmic potassium binding protein•Kbp is required for normal growth of E. coli at high K+ concentrations•Both the BON and LysM domains of Kbp are required for full K+ binding•Structural analysis indicates global conformational changes on K+ binding Ashraf et al. describe the discovery and structural analysis of a highly specific potassium binding protein, Kbp, from E. coli. Kbp is required for normal growth of E. coli at high K+ concentrations. Structural analysis shows that K+ binding induces a global conformation change in Kbp.