Effects of anticodon 2′-O-methylations on tRNA codon recognition in an Escherichia coli cell-free translation

a1 Department of Industrial Chemistry, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba 275-0016, Japan
a2 Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan


The methylation of 2′-hydroxyl groups is one of the most common posttranscriptional modifications of naturally occurring stable RNA molecules. Some tRNA species have a 2′-O-methyl nucleoside at the first position of the anticodon, and it was suggested that this modification stabilizes the codon–anticodon duplex. However, no tRNA species have been found to have the modification at the second or third position of the anticodon. In the present study, we measured the effects of anticodon 2′-O-methylation on the codon-reading efficiencies of the anticodon variants of the unmodified forms of Escherichia coli tRNA1Ser, using a cell-free protein synthesis assay. The modification of C in the first position of the anticodon into 2′-O-methylcytidine increased the efficiency of reading the G-ending codon. On the other hand, the modifications of the second and/or third positions were detrimental to the codon-reading activity. Thus, 2′-hydroxyl groups at the second and third positions of the anticodon may have some role in the translation reaction, and this may be the reason why 2′-O-methyl nucleosides are not found in these positions within natural tRNA species.

(Received January 4 2000)
(Revised January 31 2000)
(Accepted February 22 2000)

Key Words: 2′-O-methyl nucleosides; codon reading; post-transcriptional modification; ribosome; tRNA selection.

c1 Reprint requests to: Kazuyuki Takai, Department of Industrial Chemistry, Chiba Institute of Technology, 2-7-1, Tsudanuma, Narashino, Chiba 275-0016, Japan; e-mail: takai@ic.it-chiba.ac.jp.
p1 Present address: The Institute of Physical and Chemical Research (RIKEN), Hirosawa, Wako-shi, Saitama 351-0198, Japan.