Home > Publications database > The pathway to GTPase activation of elongation factor SelB on the ribosome |
Journal Article | FZJ-2017-01260 |
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2016
Nature Publ. Group
London [u.a.]
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Please use a persistent id in citations: doi:10.1038/nature20560
Abstract: In all domains of life, selenocysteine (Sec) is delivered to the ribosome by selenocysteine-specific tRNA (tRNASec) with the help of a specialized translation factor, SelB in bacteria. Sec-tRNASec recodes a UGA stop codon next to a downstream mRNA stem–loop. Here we present the structures of six intermediates on the pathway of UGA recoding in Escherichia coli by single-particle cryo-electron microscopy. The structures explain the specificity of Sec-tRNASec binding by SelB and show large-scale rearrangements of Sec-tRNASec. Upon initial binding of SelB–Sec-tRNASec to the ribosome and codon reading, the 30S subunit adopts an open conformation with Sec-tRNASec covering the sarcin–ricin loop (SRL) on the 50S subunit. Subsequent codon recognition results in a local closure of the decoding site, which moves Sec-tRNASec away from the SRL and triggers a global closure of the 30S subunit shoulder domain. As a consequence, SelB docks on the SRL, activating the GTPase of SelB. These results reveal how codon recognition triggers GTPase activation in translational GTPases.
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