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The lysosomal potassium channel TMEM175 adopts a novel tetrameric architecture

The lysosomal potassium channel TMEM175 adopts a novel tetrameric architectureTMEM175 is a lysosomal K+ channel that is important for maintaining the membrane potential and pH stability in lysosomes. It contains two homologous copies of a six-transmembrane-helix (6-TM) domain, which has no sequence homology to the canonical tetrameric K+ channels and lacks the TVGYG selectivity filter motif found in these channels. The prokaryotic TMEM175 channel, which is present in a subset of bacteria and archaea, contains only a single 6-TM domain and functions as a tetramer. Here, we present the crystal structure of a prokaryotic TMEM175 channel from Chamaesiphon minutus, CmTMEM175, the architecture of which represents a completely different fold from that of canonical K+ channels. All six transmembrane helices of CmTMEM175 are tightly packed within each subunit without undergoing domain swapping. The highly conserved TM1 helix acts as the pore-lining inner helix, creating an hourglass-shaped ion permeation pathway in the channel tetramer. Three layers of hydrophobic residues on the carboxy-terminal half of the TM1 helices form a bottleneck along the ion conduction pathway and serve as the selectivity filter of the channel. Mutagenesis analysis suggests that the first layer of the highly conserved isoleucine residues in the filter is primarily responsible for channel selectivity. Thus, the structure of CmTMEM175 represents a novel architecture of a tetrameric cation channel whose ion selectivity mechanism appears to be distinct from that of the classical K+ channel family.

Nature. 2017 Jul 27;547(7664):472-475.
doi: 10.1038/nature23269. Epub 2017 Jul 19.

 

© 2017 Macmillan Publishers Limited.

  Lee C, Guo J, Zeng W, Kim S, She J, Cang C, Ren D, Jiang Y.

Another SBC Highlight:

A domain in human EXOG converts apoptotic endonuclease to DNA-repair exonuclease

A domain in human EXOG converts apoptotic endonuclease to DNA-repair exonuclease

 

 

Nat Commun. 2017 May 3;8:14959.
doi: 10.1038/ncomms14959.

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When completing your Experimental Safety Approval Form (ESAF), please include the following in your experimental description:

 

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The on-line SBC Beamtime Request System allows users to view available beamtime on 19-ID and 19-BM, and to submit a request for rapid beamtime allocation.

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Current Beamline Statistics:

APS PDB Depositions from BioSync
SBC Sector 19 2015 2016 2017 TOTAL
ID BM ID BM ID BM
PDB Depositions 259 32 215 29 128 15 5113

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Publications Total
SBC-CAT Publication List: 19-ID 1530
SBC-CAT Publication List: 19-BM 535
SBC-CAT Publication List: ALL
APS Publications Database

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XXIV Congress and General Assembly of the International Union of Crystallography

August 21-28, 2017

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October 16-31, 2017

Cold Spring Harbor; New York, USA

 

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