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  • The EMBO Journal (2006) 25, 5942 - 5950
  • doi:10.1038/sj.emboj.7601433

Published online: 16 November 2006

Crystal structures of leucyl/phenylalanyl-tRNA-protein transferase and its complex with an aminoacyl-tRNA analog

Kyoko Suto1,a, Yoshihiro Shimizu2,a, Kazunori Watanabe1, Takuya Ueda2, Shuya Fukai3, Osamu Nureki3 and Kozo Tomita1

  1. Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
  2. Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
  3. Department of Biological Information, Graduate School of Bioscience and Technology, Tokyo Institute of Technology, Nagatsuda-cho, Midori-ku, Yokohama, Kanagawa, Japan

Correspondence to:

Kozo Tomita, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan. Tel.: +81 29 861 6085; Fax: +81 29 861 6095; E-mail: kozo-tomita@aist.go.jp

aThese authors contributed equally to this work

Received 23 June 2006; Accepted 17 October 2006

Eubacterial leucyl/phenylalanyl-tRNA protein transferase (L/F-transferase), encoded by the aat gene, conjugates leucine or phenylalanine to the N-terminal Arg or Lys residue of proteins, using Leu-tRNALeu or Phe-tRNAPhe as a substrate. The resulting N-terminal Leu or Phe acts as a degradation signal for the ClpS-ClpAP-mediated N-end rule protein degradation pathway. Here, we present the crystal structures of Escherichia coli L/F-transferase and its complex with an aminoacyl-tRNA analog, puromycin. The C-terminal domain of L/F-transferase consists of the GCN5-related N-acetyltransferase fold, commonly observed in the acetyltransferase superfamily. The p-methoxybenzyl group of puromycin, corresponding to the side chain of Leu or Phe of Leu-tRNALeu or Phe-tRNAPhe, is accommodated in a highly hydrophobic pocket, with a shape and size suitable for hydrophobic amino-acid residues lacking a branched beta-carbon, such as leucine and phenylalanine. Structure-based mutagenesis of L/F-transferase revealed its substrate specificity. Furthermore, we present a model of the L/F-transferase complex with tRNA and substrate proteins bearing an N-terminal Arg or Lys.

  • Keywords:

    • aminoacyl-tRNA,
    • N-end rule,
    • protein stability,
    • transferase