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Communicated by Ignacio Tinoco, Jr., University of California, Berkeley, CA, July 22, 2009 (received for review May 22, 2009)
Abstract
Determining the mechanism by which tRNAs rapidly and precisely transit through the ribosomal A, P, and E sites during translation remains a major goal in the study of protein synthesis. Here, we report the real-time dynamics of the L1 stalk, a structural element of the large ribosomal subunit that is implicated in directing tRNA movements during translation. Within pretranslocation ribosomal complexes, the L1 stalk exists in a dynamic equilibrium between open and closed conformations. Binding of elongation factor G (EF-G) shifts this equilibrium toward the closed conformation through one of at least two distinct kinetic mechanisms, where the identity of the P-site tRNA dictates the kinetic route that is taken. Within posttranslocation complexes, L1 stalk dynamics are dependent on the presence and identity of the E-site tRNA. Collectively, our data demonstrate that EF-G and the L1 stalk allosterically collaborate to direct tRNA translocation from the P to the E sites, and suggest a model for the release of E-site tRNA.
Footnotes
- 2To whom correspondence should be addressed. E-mail: rlg2118{at}columbia.edu
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Author contributions: J.F. and R.L.G. designed research; J.F. and R.L.S. performed research; J.E.B., J.M.H., and C.H.W. contributed new reagents/analytic tools; J.F. and J.E.B. analyzed data; and J.F. and R.L.G. wrote the paper.
The authors declare no conflict of interest.
Allosteric collaboration between elongation factor G and the ribosomal L1 stalk directs tRNA movements during translation
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