Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 103, Issue 33, Pages 12619-12624Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0601176103
Keywords
BK; gating current; MaxiK; fluorescence; voltage sensor
Categories
Funding
- NHLBI NIH HHS [HL054970, R01 HL054970] Funding Source: Medline
- NINDS NIH HHS [R01 NS043240, R01NS043240] Funding Source: Medline
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Large conductance voltage- and Ca2+-activated K+ (BKCa) channels regulate important physiological processes such as neurotransmitter release and vascular tone. BKCa channels possess a voltage sensor mainly represented by the S4 transmembrane domain. Changes in membrane potential displace the voltage sensor, producing a conformational change that leads to channel opening. By site-directed fluorescent labeling of residues in the S3-S4 region and by using voltage clamp fluorometry, we have resolved the conformational changes the channel undergoes during activation. The voltage dependence of these conformational changes (detected as changes in fluorescence emission, fluorescence vs. voltage curves) always preceded the channel activation curves, as expected for protein rearrangements associated to the movement of the voltage sensor. Extremely slow conformational changes were revealed by fluorescent labeling of position 202, elicited by a mutual interaction of the fluorophore with the adjacent tryptophan 203.
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