Journal
JOURNAL OF PHYSIOLOGICAL SCIENCES
Volume 58, Issue 6, Pages 363-369Publisher
SPRINGER TOKYO
DOI: 10.2170/physiolsci.RP007508
Keywords
MaxiK(+) channels; Rb+-induced anomalous conductance; single-channel current
Categories
Funding
- The Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan
Ask authors/readers for more resources
K+ channels permit more than one ion within their conducting pathway at any given moment and show a saturating single-file behavior. The conduction of Rb+ shows an unusual behavior, a so-called Rb+ anomaly, and it has been used to probe the mechanism of the ion conduction through K+-selective channels. Under the bi-ionic condition of K+ and Rb+, we carried out patch-clamp single-channel current measurements in MaxiK(+) channels from mouse submandibular acinar cells. Keeping only K+ on one side of the membrane while varying fractional Rb+ concentration on the opposite, we had a series of current-voltage relationships. It showed a characteristic inflection at which the ion conductance was divided into two components, one ascribed to pure K+ conduction and the other to K+ and Rb+ bi-ionic conduction. By analyzing the latter, we depicted that (1) the bi-ionic conductance showed a characteristic reduction curve as the Rb+ fractional concentration increased; (2) Rb+ can bind the channel more tightly when it accesses from the outside than from the inside. Thus we conclude that such asymmetry of the Rb+ binding determines the pattern of bi-ionic conductance reduction in K-selective channels.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available