The pathway to GTPase activation of elongation factor SelB on the ribosome.Fischer, N., Neumann, P., Bock, L.V., Maracci, C., Wang, Z., Paleskava, A., Konevega, A.L., Schroder, G.F., Grubmuller, H., Ficner, R., Rodnina, M.V., Stark, H.
(2016) Nature 540: 80-85
- PubMed: 27842381
- DOI: https://doi.org/10.1038/nature20560
- Primary Citation of Related Structures:
5LZA, 5LZB, 5LZC, 5LZD, 5LZE, 5LZF
- PubMed Abstract:
In all domains of life, selenocysteine (Sec) is delivered to the ribosome by selenocysteine-specific tRNA (tRNA Sec ) with the help of a specialized translation factor, SelB in bacteria. Sec-tRNA Sec 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-tRNA Sec binding by SelB and show large-scale rearrangements of Sec-tRNA Sec . Upon initial binding of SelB-Sec-tRNA Sec to the ribosome and codon reading, the 30S subunit adopts an open conformation with Sec-tRNA Sec 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-tRNA Sec 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.
Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.