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.

Abstract

Gating of the outward-rectifying K⁺ channel TOK1 of Saccharomyces cerevisiae is controlled by membrane voltage and extracellular K⁺ 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⁺ 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⁺. The strongest effects, with L270Y, L270F and L270W, led to more than a 30-fold decrease in apparent K⁺ 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⁺-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
• Status: Published
• Refereed: Yes
• 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: 0264-6021
• ISSN (Online): 1470-8728