Lecture 10.pdf - Building a Polypeptide The three stages of...

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Building a Polypeptide !The three stages of translation !Initiation !Elongation !Termination !All three stages require protein “factors” that aid in the translation process !Energy is provided by hydrolysis of GTP
Ribosome Association and Initiation of Translation !
Large ribosomal subunit completes the initiation complex. Met 3ʹ5ʹP+GDP P site Met Large ribosomal subunit Initiator tRNA mRNA 5ʹStart codon mRNA binding site GTP E 3ʹSmall ribosomal subunit 5ʹA 3ʹTranslation initiation complex Small ribosomal subunit binds to mRNA. i U A C 5ʹA U G 3ʹThe initiation of translation
Elongation of the Polypeptide Chain !
Amino end of polypeptide Codon recognition mRNA 5ʹP A E P site E A site 3ʹGTP GDP +P i Elongation
Amino end of polypeptide Codon recognition mRNA 5ʹPeptide bond formation P A E P A E P site E A site 3ʹGTP GDP +P i
Amino end of polypeptide Codon recognition mRNA Ribosome ready for next aminoacyl tRNA 5ʹP Translocation Peptide bond formation A E P A E P A E P site E A site 3ʹGTP GDP +P i GTP GDP +P i
Termination of Translation !
Release factor Stop codon (UAG, UAA, or UGA) Ribosome reaches a stop codon on mRNA. 3ʹ5ʹThe termination of translation
Release factor Free polypeptide Stop codon (UAG, UAA, or UGA) Ribosome reaches a stop codon on mRNA. Release factor promotes hydrolysis. 3ʹ5ʹ5ʹ3ʹ
Release factor Free polypeptide Stop codon (UAG, UAA, or UGA)

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