期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 105, 期 51, 页码 20263-20268出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0807056106
关键词
gating; ion channel; single-molecule
资金
- Canadian Institutes of Health Research [MOP-81351]
- Natural Sciences and Engineering Research Council of Canada [327201DG]
- Cancer Research Chair [202965]
- National Institutes of Health [GM30376, MH078822, F31NS054532]
- Canada Foundation for Innovation [202965]
- Fonds quebecois de la Recherche sur la Nature et les Technologies
The prokaryotic KcsA channel is gated at the helical bundle crossing by intracellular protons and inactivates at the extracellular selectivity filter. The C-terminal transmembrane helix has to undergo a conformational change for potassium ions to access the central cavity. Whereas a partial opening of the tetrameric channel is suggested to be responsible for subconductance levels of ion channels, including KcsA, a cooperative opening of the 4 subunits is postulated as the final opening step. In this study, we used single-channel fluorescence spectroscopy of KcsA to directly observe the movement of each subunit and the temporal correlation between subunits. Purified KcsA channels labeled at the C terminus near the bundle crossing have been inserted into supported lipid bilayer, and the fluorescence traces analyzed by means of a cooperative or independent Markov model. The analysis revealed that the 4 subunits do not move fully independently but instead showed a certain degree of cooperativity. However, the 4 subunits do not simply open in 1 concerted step.
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