VAMP721 conformations unmask an extended motif for K+ channel binding and gating control

Zhang, B. , Karnik, R. , Waghmare, S., Donald, N. A. and Blatt, M. R. (2017) VAMP721 conformations unmask an extended motif for K+ channel binding and gating control. Plant Physiology, 173(1), pp. 536-551. (doi:10.1104/pp.16.01549) (PMID:27821719)

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Abstract

Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins play a major role in membrane fusion and contribute to cell expansion, signaling, and polar growth in plants. The SNARE SYP121 of Arabidopsis thaliana that facilitates vesicle fusion at the plasma membrane also binds with, and regulates, K+ channels already present at the plasma membrane to affect K+ uptake and K+-dependent growth. Here, we report that its cognate partner VAMP721, which assembles with SYP121 to drive membrane fusion, binds to the KAT1 K+ channel via two sites on the protein, only one of which contributes to channel-gating control. Binding to the VAMP721 SNARE domain suppressed channel gating. By contrast, interaction with the amino-terminal longin domain conferred specificity on VAMP721 binding without influencing gating. Channel binding was defined by a linear motif within the longin domain. The SNARE domain is thought to wrap around this structure when not assembled with SYP121 in the SNARE complex. Fluorescence lifetime analysis showed that mutations within this motif, which suppressed channel binding and its effects on gating, also altered the conformational displacement between the VAMP721 SNARE and longin domains. The presence of these two channel-binding sites on VAMP721, one also required for SNARE complex assembly, implies a well-defined sequence of events coordinating K+ uptake and the final stages of vesicle traffic. It suggests that binding begins with VAMP721, and subsequently with SYP121, thereby coordinating K+ channel gating during SNARE assembly and vesicle fusion. Thus, our findings also are consistent with the idea that the K+ channels are nucleation points for SNARE complex assembly.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Blatt, Professor Michael and Zhang, Dr Ben and Karnik, Dr Rucha and Donald, Miss Naomi and Waghmare, Dr Sakharam
Authors: Zhang, B., Karnik, R., Waghmare, S., Donald, N. A., and Blatt, M. R.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Plant Physiology
Publisher:American Society of Plant Biologists
ISSN:0032-0889
ISSN (Online):1532-2548
Published Online:07 November 2016
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Plant Physiology 173(1): 536-551
Publisher Policy:Reproduced under a Creative Commons License
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
563751MAGIC - A Multi-tiered approach to generating increased carbon dioxide in the chloroplastMichael BlattBiotechnology and Biological Sciences Research Council (BBSRC)BB/I024496/1RI MOLECULAR CELL & SYSTEMS BIOLOGY
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563753MAGIC - A Multi-tiered approach to generating increased carbon dioxide in the chloroplastMichael BlattBiotechnology and Biological Sciences Research Council (BBSRC)BB/M01133X/1RI MOLECULAR CELL & SYSTEMS BIOLOGY
656891Analysing GORK clustering for enhanced stomatal controlMichael BlattBiotechnology and Biological Sciences Research Council (BBSRC)BB/M001601/1RI MOLECULAR CELL & SYSTEMS BIOLOGY
650621Developing a synthetic approach to manipulating guard cell membrane transport and stomatal controlMichael BlattBiotechnology and Biological Sciences Research Council (BBSRC)BB/L019205/1RI MOLECULAR CELL & SYSTEMS BIOLOGY