Interactive domains between pore loops of the yeast K+ channel TOK1 associate with extracellular K+ sensitivity

Johansson, I. and Blatt, M.R. (2005) Interactive domains between pore loops of the yeast K+ channel TOK1 associate with extracellular K+ sensitivity. Biochemical Journal, 393(3), pp. 645-655.

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Gating of the outward-rectifying K<sup>+</sup> channel TOK1 of Saccharomyces cerevisiae is controlled by membrane voltage and extracellular K<sup>+</sup> concentration. Previous studies identified two kinetically distinct effects of K+, and site-mutagenic analysis associated these K+-dependencies with domains of the extracellular turrets of the channel protein. We have mapped the TOK1 pore domains to extant K<sup>+</sup> channel crystal structures to target additional residues contributing to TOK1 gating. Leu270, located in the first pore domain of TOK1, was found to be critical for gating and its K+ sensitivity. Analysis of amino acid substitutions indicated that spatial position of the polypeptide backbone is a primary factor determining gating sensitivity to K<sup>+</sup>. The strongest effects, with L270Y, L270F and L270W, led to more than a 30-fold decrease in apparent K<sup>+</sup> affinity and an inversion in the apparent K+-dependence of voltage-dependent gating compared with the wild-type current. A partial rescue of wild-type gating was obtained on substitution in the second pore domain with the double mutant L270D/A428Y. These, and additional results, demarcate extracellular domains that are associated with the K<sup>+</sup>-sensitivity of TOK1 and they offer primary evidence for a synergy in gating between the two pore domains of TOK1, demonstrating an unexpected degree of long-distance interaction across the mouth of the K+ channel.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Blatt, Professor Michael
Authors: Johansson, I., and Blatt, M.R.
Subjects:Q Science > QH Natural history > QH345 Biochemistry
College/School:College of Medical Veterinary and Life Sciences
Journal Name:Biochemical Journal
Publisher:Portland Press Ltd.
ISSN (Online):1470-8728

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