Structural basis for potassium transport in prokaryotes by KdpFABC
Marie Sweet, Casper K. Larsen, Xihui Zhang, Michael Schlame, Bjørn Panyella Pedersen, David L. Stokes
Abstract
Significance Potassium is the major intracellular cation in all kingdoms of life. In bacteria, potassium is used to maintain membrane potential, pH, and to provide turgor pressure for cell growth and division. When external potassium levels are low, an ATP-dependent pump called KdpFABC is essential to maintain intracellular potassium levels. This protein complex comprises a subunit descending from potassium channels and another from P-type ATPases. We used cryogenic electron microscopy to investigate this unique partnership and to address mechanisms of energy coupling and transport. We present structures corresponding to all major reaction intermediates and map distinct densities along the proposed transport pathway. Based on this data, we describe a mechanism that is unique amongst known membrane transporters.