Binding of kappa-conotoxin PVIIA to Shaker K+ channels reveals different K+ and Rb+ occupancies within the ion channel pore

The Journal of General Physiology
A BoccaccioH Terlau

Abstract

The x-ray structure of the KcsA channel at different [K(+)] and [Rb(+)] provided insight into how K(+) channels might achieve high selectivity and high K(+) transit rates and showed marked differences between the occupancies of the two ions within the ion channel pore. In this study, the binding of kappa-conotoxin PVIIA (kappa-PVIIA) to Shaker K(+) channel in the presence of K(+) and Rb(+) was investigated. It is demonstrated that the complex results obtained were largely rationalized by differences in selectivity filter occupancy of this 6TM channels as predicted from the structural work on KcsA. kappa-PVIIA inhibition of the Shaker K(+) channel differs in the closed and open state. When K(+) is the only permeant ion, increasing extracellular [K(+)] decreases kappa-PVIIA affinity for closed channels by decreasing the "on" binding rate, but has no effect on the block of open channels, which is influenced only by the intracellular [K(+)]. In contrast, extracellular [Rb(+)] affects both closed- and open-channel binding. As extracellular [Rb(+)] increases, (a) binding to the closed channel is slightly destabilized and acquires faster kinetics, and (b) open channel block is also destabilized and the lowest block seems to occur when...Continue Reading

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Citations

Dec 2, 2004·The Journal of General Physiology·Toby W AllenBenoit Roux
Sep 6, 2006·Toxicon : Official Journal of the International Society on Toxinology·Raymond S Norton, Baldomero M Olivera
Jul 15, 2005·The Journal of Pharmacology and Experimental Therapeutics·Shi-Bing YangMarjan Rupnik
Apr 20, 2016·Biotechnology and Bioengineering·Soohyun KwonDavid J Craik
Mar 27, 2013·Marine Drugs·M Harunur RashidSerdar Kuyucak

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Methods Mentioned

BETA
electron paramagnetic resonance

Software Mentioned

Igor
Pulse + PulseFit

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