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PROKARYOTIC TRANSLATION - tRNA is modified it contains a...

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PROKARYOTIC TRANSLATION In E. coli and other prokaryotes the mRNA is transcribed without prior processing. But translation does not start directly at the 5' end of the mRNA. Instead we find an untranslated region at the 5' end called 5' untranslated region or 5' UTR . Translation always starts with the amino acid methionine and therefore usually at an AUG codon: All newly synthesized proteins contain a methionine at their amino terminus (often cleaved off after synthesis). In E. coli and many other prokaryotes the tRNA for methionine at start of translation different from the tRNAMet used in the middle of the coding sequence: specific initiator tRNA . And additionally the methionine contained in the initiator
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Unformatted text preview: tRNA is modified, it contains a formyl group at its amino (N) group ( N-formylmethionine ): tRNAfMet . In prokaryotic mRNA, the first AUG at the 5' end is not necessarily the start site for translation. Instead the start codon is always preceeded by a sequence specifying the AUG as start site. The specific sequence ( AGGAGGU ) is called Shine-Dalgarno sequence after its discoverers. The sequence base pairs with a complementary sequence near the 3' terminus in the 16S rRNA (part of the small, 30S ribosomal subunit). This specific base pairing alines the mRNA and the ribosome....
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