12BIS1012013TranslatLect12

In prokaryotes translation initiates with a specially

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Unformatted text preview: mentarity (like shRNA), enables tRNA to adopt a Intramolecular complex, double helical structure. The 3-D structure of tRNA indicate that it is not a cloverleaf structure but rather an upside down “L” structure with stress and unusual hydrogen bonds. stress BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 22 L-Form Structure of tRNA BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 23 Two Methionine tRNAs ­ ­ ­ ­ ­ All prokaryotic and eukaryotic translation begins with methionine, All although this amino acid may be removed after translation terminates. In prokaryotes, translation initiates with a specially modified In methionine called "formyl-methionine." This special methionine is methionine This required for the formation of the pre-initiation complex. pre-initiation Since methionine codons frequently occur in mRNAs, how does the Since cell prevent the incorporation of f-met within the growing polypetide? cell Special structural modifications on the tRNAf-met make it recognizable by initiation factor 2 (IF2) and by methionyl transformylase, the by and methionyl the enzyme responsible for formylating methionine. Since IF2 can only recognize the spec...
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