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Published April 13, 1999 | Published
Journal Article Open

Location of translational initiation factor IF3 on the small ribosomal subunit

Abstract

The location of translational initiation factor IF3 bound to the 30S subunit of the Thermus thermophilus ribosome has been determined by cryoelectron microscopy. Both the 30S⋅IF3 complex and control 30S subunit structures were determined to 27-Å resolution. The difference map calculated from the two reconstructions reveals three prominent lobes of positive density. The previously solved crystal structure of IF3 fits very well into two of these lobes, whereas the third lobe probably arises from conformational changes induced in the 30S subunit as a result of IF3 binding. Our placement of IF3 on the 30S subunit allows an understanding in structural terms of the biochemical functions of this initiation factor, namely its ability to dissociate 70S ribosomes into 30S and 50S subunits and the preferential selection of initiator tRNA by IF3 during initiation.

Additional Information

© 1999 National Academy of Sciences. Communicated by Peter B. Moore, Yale University, New Haven, CT (received for review January 7, 1999) We thank Amy B. Heagle for help with illustrations and Irene S. Gabashvili for help with some of the computation. This work was supported by National Institutes of Health grant R01GM 44973 (to V.R. and Stephen W. White) and R37GM 29169 and R01GM 55440 (to J.F.). The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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Created:
August 22, 2023
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October 18, 2023