The first amino acid added to a polypeptide is methionine but it will have internal methionines as well. Why are separate tRNAs for methionine used for translation initiation and elongation, and how are they distinguished by the ribosome?
What will be an ideal response?
Ans: The first initiator tRNA must bind the partial P site on the 30S subunit and is recognized by a specific factor, IF-2. During elongation, methionyl-tRNAs enter the full A site on ribosomes and are bound by EF-Tu. The methionine on the initiator tRNA is formylated on the amino group and the tRNAfMet has slightly altered base pairing of the acceptor and anticodon stems compared to the tRNAmMet.
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