Conformational heterogeneity in closed and open states of the KcsA potassium channel in lipid bicelles Academic Article uri icon

Overview

MeSH Major

  • Bacterial Proteins
  • Cyclic AMP
  • Ion Channel Gating
  • Membrane Lipids
  • Mesorhizobium
  • Potassium Channels
  • Recombinant Fusion Proteins

abstract

  • The process of ion channel gating-opening and closing-involves local and global structural changes in the channel in response to external stimuli. Conformational changes depend on the energetic landscape that underlies the transition between closed and open states, which plays a key role in ion channel gating. For the prokaryotic, pH-gated potassium channel KcsA, closed and open states have been extensively studied using structural and functional methods, but the dynamics within each of these functional states as well as the transition between them is not as well understood. In this study, we used solution nuclear magnetic resonance (NMR) spectroscopy to investigate the conformational transitions within specific functional states of KcsA. We incorporated KcsA channels into lipid bicelles and stabilized them into a closed state by using either phosphatidylcholine lipids, known to favor the closed channel, or mutations designed to trap the channel shut by disulfide cross-linking. A distinct state, consistent with an open channel, was uncovered by the addition of cardiolipin lipids. Using selective amino acid labeling at locations within the channel that are known to move during gating, we observed at least two different slowly interconverting conformational states for both closed and open channels. The pH dependence of these conformations and the predictable disruptions to this dependence observed in mutant channels with altered pH sensing highlight the importance of conformational heterogeneity for KcsA gating.

publication date

  • January 2016

Research

keywords

  • Academic Article

Identity

Language

  • eng

PubMed Central ID

  • PMC4969796

Digital Object Identifier (DOI)

  • 10.1085/jgp.201611602

PubMed ID

  • 27432996

Additional Document Info

start page

  • 119

end page

  • 32

volume

  • 148

number

  • 2