The Mechanism of Translation :

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The Mechanism of Translation ? Initiation
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Content
Dissociation of Ribosomes Formation of the
Initiation Complex
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Dissociation of Ribosomes
Predict-ribosomes dissociate-why? Why do
ribosomes must dissociate? How to prove that
dissociation occurs? Experimental plan to
demonstrate subunit exchange. Demonstration of
ribosomal subunit exchange.
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How to dissociate
Previously experiment Discover of initiation
factor Predict-initiation factors help to
dissociate-why? Experiment1 measure the relative
amounts Experiment2 Binding of IF-3 to 30S
ribosomal subunits. Experiment3 Assay for
ribosome dissociation. The real situation.
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Formation of the Initiation Complex
The first codon and the first aminoacyl
tRNA Some experiment about the Initiation
Complex
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Summary
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Thanks!
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The first codon
Previously experiment Something
special Problem A. The condon they respond to.
B. The positions they placed.
Return to Initiation Complex
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Experiment of the Initiation Complex
Factor cause binding IF-2 cannot bind
itself GTP binds to the 30S ribosomal GTP
hydrolyze and release IF-2
Return to Initiation Complex
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Why do ribosomes must dissociate?
Ribosomes consist of two subunits. Both
prokaryotic and eukaryotic cells build
translation initiation complexes on the small
ribosomal subunit.
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Dissociation require outside agents

• Few biological reactions occur spontaneously.
• Severo Ochoa and his colleagues isolated
• the initiation factors in 1966 by washing
• ribosomes with buffers of progressively
• higher salt concentration.

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