Structures of tRNAs with an expanded anticodon loop in the decoding center of the 30S ribosomal subunit

  1. Christine M. Dunham1,4,
  2. Maria Selmer1,4,5,
  3. Steven S. Phelps2,
  4. Ann C. Kelley1,
  5. Tsutomu Suzuki3,
  6. Simpson Joseph2, and
  7. V. Ramakrishnan1
  1. 1MRC-Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom
  2. 2Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0314, USA
  3. 3Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, 113-8656, Japan

  1. ↵4 These authors contributed equally to this work.

Abstract

During translation, some +1 frameshift mRNA sites are decoded by frameshift suppressor tRNAs that contain an extra base in their anticodon loops. Similarly engineered tRNAs have been used to insert nonnatural amino acids into proteins. Here, we report crystal structures of two anticodon stem–loops (ASLs) from tRNAs known to facilitate +1 frameshifting bound to the 30S ribosomal subunit with their cognate mRNAs. ASLCCCG and ASLACCC (5′–3′ nomenclature) form unpredicted anticodon–codon interactions where the anticodon base 34 at the wobble position contacts either the fourth codon base or the third and fourth codon bases. In addition, we report the structure of ASLACGA bound to the 30S ribosomal subunit with its cognate mRNA. The tRNA containing this ASL was previously shown to be unable to facilitate +1 frameshifting in competition with normal tRNAs (Hohsaka et al. 2001), and interestingly, it displays a normal anticodon–codon interaction. These structures show that the expanded anticodon loop of +1 frameshift promoting tRNAs are flexible enough to adopt conformations that allow three bases of the anticodon to span four bases of the mRNA. Therefore it appears that normal triplet pairing is not an absolute constraint of the decoding center.

Keywords

Footnotes

  • ↵5 Present address: Department of Cell and Molecular Biology, BMC, Uppsala University, Box 596, SE-75124 Uppsala, Sweden.

  • Reprint requests to: Simpson Joseph, Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0314, USA; e-mail: sjoseph{at}chem.ucsd.edu; or V. Ramakrishnan, MRC-Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom; e-mail: ramak{at}mrc-lmb.cam.ac.uk; fax: 44-1223-123456.

  • Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.367307.

    • Received November 1, 2006.
    • Accepted February 15, 2007.

This Article

  1. Published in Advance April 6, 2007, doi: 10.1261/rna.367307 RNA 2007. Copyright © 2007 RNA Society

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