Unformatted text preview: sequence are two additional
sequences that play important roles in the initiation of
translation. These are the SD site (Shine Dalgarno) and
methionine codon, ATG (or AUG in the mRNA).
The SD site, also referred to as the ribosome binding site
(RBS), is required for aligning the mRNA on the 30S subunit
of the ribosome. This is accomplished by hydrogen bonding
between the SD site on the mRNA and complementary
sequences at the 3' end of the 16S rRNA in the 30S subunit.
Once aligned, the methionine codon (AUG) is placed such
that when bound by the aminoacyl methionine-charged tRNA,
the methionine will be over the P site on the 50S subunit.
site BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013
BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 37 Shine Dalgarno Sites in Prokaryotic mRNAs
These SD sites in prokaryotes are conserved. Shown below
are 8 SD sites that have been used to generate the
consensus sequence 5’-AGGAGG-3’
consensus BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodrigu...
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