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Conformational changes in switch I of EF‐G drive its directional cycling on and off the ribosome
Author(s) -
Ticu Cristina,
Nechifor Roxana,
Nguyen Boray,
Desrosiers Melanie,
Wilson Kevin S
Publication year - 2009
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2009.169
Subject(s) - biology , cycling , ribosome , translation (biology) , conformational change , biophysics , microbiology and biotechnology , genetics , rna , messenger rna , gene , history , archaeology
We have trapped elongation factor G (EF‐G) from Escherichia coli in six, functionally defined states, representing intermediates in its unidirectional catalytic cycle, which couples GTP hydrolysis to tRNA–mRNA translocation in the ribosome. By probing EF‐G with trypsin in each state, we identified a substantial conformational change involving its conserved switch I (sw1) element, which contacts the GTP substrate. By attaching FeBABE (a hydroxyl radical generating probe) to sw1, we could monitor sw1 movement (by ∼20 Å), relative to the 70S ribosome, during the EF‐G cycle. In free EF‐G, sw1 is disordered, particularly in GDP‐bound and nucleotide‐free states. On EF‐G•GTP binding to the ribosome, sw1 becomes structured and tucked inside the ribosome, thereby locking GTP onto EF‐G. After hydrolysis and translocation, sw1 flips out from the ribosome, greatly accelerating release of GDP and EF‐G from the ribosome. Collectively, our results support a central role of sw1 in driving the EF‐G cycle during protein synthesis.