Protein-based peptide-bond formation by aminoacyl-tRNA protein transferase |
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Authors: | Watanabe Kazunori Toh Yukimatsu Suto Kyoko Shimizu Yoshihiro Oka Natsuhisa Wada Takeshi Tomita Kozo |
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Affiliation: | Institute of Biological Resources and Functions, National Institute of Advanced Industrial Sciences and Technology, 1-1-1, Higashi, Tsukuba-shi, Ibaraki 305-8566, Japan. |
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Abstract: | Eubacterial leucyl/phenylalanyl-tRNA protein transferase (LF-transferase) catalyses peptide-bond formation by using Leu-tRNA(Leu) (or Phe-tRNA(Phe)) and an amino-terminal Arg (or Lys) of a protein, as donor and acceptor substrates, respectively. However, the catalytic mechanism of peptide-bond formation by LF-transferase remained obscure. Here we determine the structures of complexes of LF-transferase and phenylalanyl adenosine, with and without a short peptide bearing an N-terminal Arg. Combining the two separate structures into one structure as well as mutation studies reveal the mechanism for peptide-bond formation by LF-transferase. The electron relay from Asp 186 to Gln 188 helps Gln 188 to attract a proton from the alpha-amino group of the N-terminal Arg of the acceptor peptide. This generates the attacking nucleophile for the carbonyl carbon of the aminoacyl bond of the aminoacyl-tRNA, thus facilitating peptide-bond formation. The protein-based mechanism for peptide-bond formation by LF-transferase is similar to the reverse reaction of the acylation step observed in the peptide hydrolysis reaction by serine proteases. |
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