Publication Date:
2010-07-09
Description:
The coupled interplay between activation and inactivation gating is a functional hallmark of K(+) channels. This coupling has been experimentally demonstrated through ion interaction effects and cysteine accessibility, and is associated with a well defined boundary of energetically coupled residues. The structure of the K(+) channel KcsA in its fully open conformation, in addition to four other partial channel openings, richly illustrates the structural basis of activation-inactivation gating. Here, we identify the mechanistic principles by which movements on the inner bundle gate trigger conformational changes at the selectivity filter, leading to the non-conductive C-type inactivated state. Analysis of a series of KcsA open structures suggests that, as a consequence of the hinge-bending and rotation of the TM2 helix, the aromatic ring of Phe 103 tilts towards residues Thr 74 and Thr 75 in the pore-helix and towards Ile 100 in the neighbouring subunit. This allows the network of hydrogen bonds among residues Trp 67, Glu 71 and Asp 80 to destabilize the selectivity filter, allowing entry to its non-conductive conformation. Mutations at position 103 have a size-dependent effect on gating kinetics: small side-chain substitutions F103A and F103C severely impair inactivation kinetics, whereas larger side chains such as F103W have more subtle effects. This suggests that the allosteric coupling between the inner helical bundle and the selectivity filter might rely on straightforward mechanical deformation propagated through a network of steric contacts. Average interactions calculated from molecular dynamics simulations show favourable open-state interaction-energies between Phe 103 and the surrounding residues. We probed similar interactions in the Shaker K(+) channel where inactivation was impaired in the mutant I470A. We propose that side-chain rearrangements at position 103 mechanically couple activation and inactivation in KcsA and a variety of other K(+) channels.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3033755/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3033755/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cuello, Luis G -- Jogini, Vishwanath -- Cortes, D Marien -- Pan, Albert C -- Gagnon, Dominique G -- Dalmas, Olivier -- Cordero-Morales, Julio F -- Chakrapani, Sudha -- Roux, Benoit -- Perozo, Eduardo -- R01 GM057846/GM/NIGMS NIH HHS/ -- R01 GM057846-15/GM/NIGMS NIH HHS/ -- R01 GM062342/GM/NIGMS NIH HHS/ -- R01 GM062342-05/GM/NIGMS NIH HHS/ -- R01-GM57846/GM/NIGMS NIH HHS/ -- R01-GM62342/GM/NIGMS NIH HHS/ -- England -- Nature. 2010 Jul 8;466(7303):272-5. doi: 10.1038/nature09136.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20613845" target="_blank"〉PubMed〈/a〉
Keywords:
Allosteric Regulation
;
Bacterial Proteins/*chemistry/genetics/*metabolism
;
Cysteine/genetics/metabolism
;
Electron Spin Resonance Spectroscopy
;
Humans
;
Hydrogen Bonding
;
*Ion Channel Gating
;
Kinetics
;
Models, Molecular
;
Molecular Dynamics Simulation
;
Phenylalanine/metabolism
;
Potassium Channels/*chemistry/genetics/*metabolism
;
Protein Conformation
;
Shaker Superfamily of Potassium Channels/chemistry/genetics/metabolism
;
Streptomyces lividans/*chemistry
;
Structure-Activity Relationship
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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