Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 110, Issue 2, Pages 749-754Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1217323110
Keywords
fluorescence measurements; single-channel current; gating kinetics; pH-dependence; activation gate
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Funding
- Japanese Ministry of Education, Culture, Sports, Science, and Technology [23370067, 21107508, 21657038, 20247016, 11020017]
- Grants-in-Aid for Scientific Research [23370067, 24659096, 21657038, 20247016, 21107508] Funding Source: KAKEN
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Membrane lipids modulate the function of membrane proteins. In the case of ion channels, they bias the gating equilibrium, although the underlying mechanism has remained elusive. Here we demonstrate that the N-terminal segment (M0) of the KcsA potassium channel mediates the effect of changes in the lipid milieu on channel gating. The M0 segment is a membrane-anchored amphipathic helix, bearing positively charged residues. In asymmetric membranes, the M0 helix senses the presence of negatively charged phospholipids on the inner leaflet. Upon gating, the M0 helix revolves around the axis of the helix on the membrane surface, inducing the positively charged residues to interact with the negative head groups of the lipids so as to stabilize the open conformation (i.e., the roll-and-stabilize model). The M0 helix is thus a charge-sensitive antenna, capturing temporary changes in lipid composition in the fluidic membrane. This unique type of sensory device may be shared by various types of membrane proteins.
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