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Title: Crystal structure of the potassium-importing KdpFABC membrane complex

Abstract

Cellular potassium import systems play a fundamental role in osmoregulation, pH homeostasis and membrane potential in all domains of life. In bacteria, the kdp operon encodes a four-subunit potassium pump that maintains intracellular homeostasis, cell shape and turgor under conditions in which potassium is limiting1. This membrane complex, called KdpFABC, has one channel-like subunit (KdpA) belonging to the superfamily of potassium transporters and another pump-like subunit (KdpB) belonging to the superfamily of P-type ATPases. Although there is considerable structural and functional information about members of both superfamilies, the mechanism by which uphill potassium transport through KdpA is coupled with ATP hydrolysis by KdpB remains poorly understood. Here we report the 2.9 Å X-ray structure of the complete Escherichia coli KdpFABC complex with a potassium ion within the selectivity filter of KdpA and a water molecule at a canonical cation site in the transmembrane domain of KdpB. The structure also reveals two structural elements that appear to mediate the coupling between these two subunits. Specifically, a protein-embedded tunnel runs between these potassium and water sites and a helix controlling the cytoplasmic gate of KdpA is linked to the phosphorylation domain of KdpB. On the basis of these observations, we propose amore » mechanism that repurposes protein channel architecture for active transport across biomembranes.« less

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NIHFOREIGNOTHER
OSTI Identifier:
1375361
Resource Type:
Journal Article
Journal Name:
Nature (London)
Additional Journal Information:
Journal Volume: 546; Journal Issue: 7660; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; x-ray crystallography; potassium channels; potassium; membrane proteins

Citation Formats

Huang, Ching-Shin, Pedersen, Bjørn Panyella, and Stokes, David L. Crystal structure of the potassium-importing KdpFABC membrane complex. United States: N. p., 2017. Web. doi:10.1038/nature22970.
Huang, Ching-Shin, Pedersen, Bjørn Panyella, & Stokes, David L. Crystal structure of the potassium-importing KdpFABC membrane complex. United States. doi:10.1038/nature22970.
Huang, Ching-Shin, Pedersen, Bjørn Panyella, and Stokes, David L. Wed . "Crystal structure of the potassium-importing KdpFABC membrane complex". United States. doi:10.1038/nature22970.
@article{osti_1375361,
title = {Crystal structure of the potassium-importing KdpFABC membrane complex},
author = {Huang, Ching-Shin and Pedersen, Bjørn Panyella and Stokes, David L.},
abstractNote = {Cellular potassium import systems play a fundamental role in osmoregulation, pH homeostasis and membrane potential in all domains of life. In bacteria, the kdp operon encodes a four-subunit potassium pump that maintains intracellular homeostasis, cell shape and turgor under conditions in which potassium is limiting1. This membrane complex, called KdpFABC, has one channel-like subunit (KdpA) belonging to the superfamily of potassium transporters and another pump-like subunit (KdpB) belonging to the superfamily of P-type ATPases. Although there is considerable structural and functional information about members of both superfamilies, the mechanism by which uphill potassium transport through KdpA is coupled with ATP hydrolysis by KdpB remains poorly understood. Here we report the 2.9 Å X-ray structure of the complete Escherichia coli KdpFABC complex with a potassium ion within the selectivity filter of KdpA and a water molecule at a canonical cation site in the transmembrane domain of KdpB. The structure also reveals two structural elements that appear to mediate the coupling between these two subunits. Specifically, a protein-embedded tunnel runs between these potassium and water sites and a helix controlling the cytoplasmic gate of KdpA is linked to the phosphorylation domain of KdpB. On the basis of these observations, we propose a mechanism that repurposes protein channel architecture for active transport across biomembranes.},
doi = {10.1038/nature22970},
journal = {Nature (London)},
issn = {0028-0836},
number = 7660,
volume = 546,
place = {United States},
year = {2017},
month = {6}
}

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