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