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Crystal structures of the human elongation factor eEFSec suggest a non-canonical mechanism for selenocysteine incorporation

Crystal structures of the human elongation factor eEFSec suggest a non-canonical mechanism for selenocysteine incorporationSelenocysteine is the only proteinogenic amino acid encoded by a recoded in-frame UGA codon that does not operate as the canonical opal stop codon. A specialized translation elongation factor, eEFSec in eukaryotes and SelB in prokaryotes, promotes selenocysteine incorporation into selenoproteins by a still poorly understood mechanism. Our structural and biochemical results reveal that four domains of human eEFSec fold into a chalice-like structure that has similar binding affinities for GDP, GTP and other guanine nucleotides. Surprisingly, unlike in eEF1A and EF-Tu, the guanine nucleotide exchange does not cause a major conformational change in domain 1 of eEFSec, but instead induces a swing of domain 4. We propose that eEFSec employs a non-canonical mechanism involving the distinct C-terminal domain 4 for the release of the selenocysteinyl-tRNA during decoding on the ribosome.

Nat Commun. 2016 Oct 6;7:12941.
doi: 10.1038/ncomms12941.

© 2016 Macmillan Publishers Limited, part of Springer Nature.

  Dobosz-Bartoszek M, Pinkerton MH, Otwinowski Z, Chakravarthy S, Söll D, Copeland PR, Simonović M.

Another SBC Highlight:

Bile salt receptor complex activates a pathogenic type III secretion system
NPAS1-ARNT and NPAS3-ARNT crystal structures implicate the bHLH-PAS family as multi-ligand binding transcription factors.


Many bHLH-PAS proteins are significantly involved in human disease processes and would be ideal drug targets if their architectures could accommodate binding and modulation by small-molecules.



Elife. 2016 Oct 26;5. pii: e18790.
doi: 10.7554/eLife.18790.

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SBC Announcements:


19-ID Pilatus Detector


SBC has implemented a Pilatus 3 X 6M detector into the User Program at beamline 19-ID. Data collected by our users has been of outstanding quality.



19-BM Robotic sample mounter available


A robot is now available for use at beamline 19-BM. The sample dewar accommodates ten Unipuck magazines; pins must be 18mm in length and use either SSRL or ALS bases. Experienced users may now request remote access to 19-BM when applying for beamtime.



SBC Staff Hosting Changes


SBC staff are now available for User Support between the hours of 8:00am and 10:pm.




ALSO: Please Be Aware...!


APS requests the Experimental Safety Approval Form (ESAF) be submitted at least seven days prior to your scheduled beamtime.


Failure to submit your ESAF in advance may result in delaying the beginning of your experiment.


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If you have any suggestions or comments, please feel free to e-mail us.


Rapid Access Beamtime Available:

SBC Beamtime Request System

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.

Beamtime is available to the research community via a peer reviewed proposal system; it is supported by the U.S. Department of Energy, Office of Biological and Environmental Research.

Current Beamline Statistics:

APS PDB Depositions from BioSync
SBC Sector 19 2014 2015 2016 TOTAL
PDB Depositions 263 36 257 31 125 21 4872

APS Publications Database:

Publications Total
SBC-CAT Publication List: 19-ID 1450
SBC-CAT Publication List: 19-BM 525
SBC-CAT Publication List: ALL
APS Publications Database

MCSG / APCF Announcements:


Beginning August 01, 2015 the Midwest Center for Structural Genomics (MCSG) will start accepting applications for access to the MCSG User Resource.


MCSG's structure determination platform is well established, and combines technologies, robotics and expertise for gene cloning, protein production, and crystallization, as well as biochemical and biophysical characterization.


For further information, please contact Andrzej Joachimiak.


Future Meetings:


DLS-CCP4 Data Collection and Structure Solution Workshop

December 13-20, 2016

Diamond Light Source; Oxfordshire, UK


CCP4 Study Weekend 2017

January 9-11, 2017

East Midlands Conference Centre; Nottingham University, UK


XXIII West Coast Protein Crystallography Workshop

March 19-22, 2017

Pacific Grove; California, USA


SBC Beamline Phone Numbers:

Phone Location Number
19-ID Beamline Control Station 630-252-9823
19-ID Beamline Cordless Phone 630-252-0569
19-ID Beamline Inside D-Hutch 630-252-1819
19-BM Beamline Control Station 630-252-9833
19-BM Beamline Cordless Phone 630-252-0568
19-BM Beamline Inside D-Hutch 630-252-1719