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| S8 protein |
-ribosomal protein S8 binds 16S rRNA and own mRNA
-translation repressed only when need for S8 protein satisfied |
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mcs5109 Thu, 23 Oct 2008 05:42:01 GMT |
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| Ribosomal Proteins repress own synthesis?! |
-have to regulate own growth rate
-operon expression regulated by ribosome []
-ribosomal proteins bind to the mRNA near the start site operon genes
-prevents ribosomes from binding |
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mcs5109 Thu, 23 Oct 2008 05:42:01 GMT |
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| What if Protein or RNA binds near the ribosome-binding site? |
-negatively regulates bacterial translation initiation
-want to impair association of mRNA with 16S rRNA of 30S subunit
-or, mRNA binds with self to mask RBS units |
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mcs5109 Thu, 23 Oct 2008 05:28:31 GMT |
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| translation regulation |
-gene expression mostly regulated at transcription level b/c very effective
-responds rapdly to external signals (skip the time required to mRNA transcription, RNA processing and/or mRNA transport to the cytoplasm)
-typically stops at initiation |
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mcs5109 Thu, 23 Oct 2008 05:28:31 GMT |
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| Puromycin |
-antibiotic that kills bacteria
-binds in the A site
-participates in peptide bond formation
-diffuse out of ribosome
-peptides dissociate from ribosome as incomplete |
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mcs5109 Thu, 23 Oct 2008 05:21:35 GMT |
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| How do antibiotics work? |
~40 % of the known antibiotics are inhibitors of the translational machinery |
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mcs5109 Thu, 23 Oct 2008 05:21:35 GMT |
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| Ribosome recycling factor (RRF) |
-uses EF-G and IF3 to recycle ribosome |
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mcs5109 Thu, 23 Oct 2008 05:21:35 GMT |
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| Class I release factors resemble... |
...tRNA
-anticodon
-GGQ motif that reaches into the peptidyl transferase center
-cleavage mechanism not understood |
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mcs5109 Thu, 23 Oct 2008 05:21:35 GMT |
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| Class II RFs |
(prokaryote: RF3; eukaryote: eRF3)
-GTP-reguated
-stimulate the dissociation of the class I RF form the ribosome after release of the polypeptide chain
-binds only after polypeptide release
-drives the dissociation of the class I release factor |
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mcs5109 Thu, 23 Oct 2008 05:14:13 GMT |
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| RF1 and RF2 |
-recognize different release factors
-both recognize UAA (most common) |
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mcs5109 Thu, 23 Oct 2008 05:10:47 GMT |
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| eRF1 |
-euk release factor recognizes all 3 stop codons |
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mcs5109 Thu, 23 Oct 2008 05:10:47 GMT |
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| Class I release factors (RFs) |
-recognize stop codons and trigger hydrolysis of the peptide chain
-stimulates polypeptide release through a GGQ motif |
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mcs5109 Thu, 23 Oct 2008 05:13:09 GMT |
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