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7 Cards in this Set
- Front
- Back
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What are the 3 initiation factors required for initiation of translation in E. coli and what does each one do?
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IF-1: assists in IF-3 binding
IF-2 (and GTP): binds initiator tRNA IF-3: Releases mRNA and tRNA from 30S and helps the new mRNA bind |
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What are the general steps of translation initiation in E. coli?
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1) IF3 binds to small ribosomal subunit (30S) causing the large (50S) and small subunits to dissociate.
2) IF1 binds to the small subunit and mRNA is loaded onto the small subunit (the 16S part). 3) IF2 (with bound GTP) binds to FMet-tRNA and delivers it to the ribosomal start site on mRNA. 4) 50S subunit clamps down which causes the dissocation the initiation factors and the GTP on IF2 is hydrolyzed. |
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What are the 3 elongation factors required for elongation during translation in E. coli and what does each one do?
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EF-Tu: Uses GTP to bring aminoacyl-tRNA to a free site on the ribosome.
EF-Ts: Displaces GDP from EF-Tu (just takes GDP out of EF-Tu). EF-G: Promotes translocation through GTP binding and hydrolysis (Uses GTP hydrolysis to drive the reaction forward by mechanically moving mRNA & tRNA through) |
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What are the 2 release factors to know in regard to translation in E. coli and what do they do?
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RF-3: Stimulates RF-1/RF-2 release via GTP hydrolysis
RRF: (Ribosomal Release Factor) Together with EF-G, causes the release of mRNA (still bound to tRNA) from the ribosome. |
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What are the basic steps of elongation during translation in E. coli?
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1) Aminoacyl-tRNA binding
2) Transpeptidation 3) Translocation |
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How do each of these inhibitors work?
1) Erythromycin 2) Tetracycline 3) Puromycin 4) Diptheria toxin |
1) Erythromycin inhibits translocation by the prokaryotic large subunit.
2) Tetracycline inhibits aminoacyl-tRNA binding to the prokaryotic small subunit. (T for aminacyl-tRNA!) 3) Puromycin causes premature chain termination (P for premature!) 4) Diphtheria inactivates eEF2 by ADP-ribosylation |
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What are the two important eukaryotic initiation factors to remember and what do they do?
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eIF2: it functions like bacterial IF2, it recruits the initiator Met-tRNA. Like IF2, it requires GTP to be bound!!
eIF4: it binds to the 5'cap (requires ATP!!). It scans mRNA looking for the intiation codon (AUG), this uses multiple ATPs. |
