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キーワード:
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要旨:
The functional centers of the ribosome in all organisms
contain ribosomal RNA (rRNA) modifications,
which are introduced by specialized enzymes and
come at an energy cost for the cell. Surprisingly,
none of the modifications tested so far was essential
for growth and hence the functional role of modifications
is largely unknown. Here, we show that the
methyl groups of nucleosides m2G966 and m5C967
of 16S rRNA in Escherichia coli are important for
bacterial fitness. In vitro analysis of all phases of
translation suggests that the m2G966/m5C967 modifications
are dispensable for elongation, termination
and ribosome recycling. Rather, the modifications
modulate the early stages of initiation by stabilizing
the binding of fMet-tRNAfMet to the 30S pre-initiation
complex prior to start-codon recognition. We
propose that the m2G966 and m5C967 modifications
help shaping the bacterial proteome, most likely by
fine-tuning the rates that determine the fate of a
given messenger RNA (mRNA) at early checkpoints
of mRNA selection.
