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| A Cycle of Peptide Bond Formation Consumes... |
1 ATP (adenylylation of amino acid to charge tRNA) and 2 GTP (GTP hydrolysis is spent to ensure the accuracy and order of events) |
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mcs5109 Thu, 23 Oct 2008 04:30:00 GMT |
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| EF-Ts |
-GTP exchange factor for EF-Tu |
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mcs5109 Thu, 23 Oct 2008 04:28:35 GMT |
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| EF-Tu and GTP |
-elongation factor EF-Ts acts as a GTP exchange factor for EF-Tu |
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mcs5109 Thu, 23 Oct 2008 04:28:35 GMT |
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| EF-G and GTP |
-EF-G: GDP has a low affinity for EF-G
-rapidly released after hydrolysis |
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mcs5109 Thu, 23 Oct 2008 04:28:35 GMT |
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| structures |
structure of EF-G-GDP is very similar to that of EF-Tu-GTP-tRNA complex |
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mcs5109 Thu, 23 Oct 2008 04:28:35 GMT |
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| E site |
-no codon:anticodon interaction
-no affinity, so tRNA released |
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mcs5109 Thu, 23 Oct 2008 04:28:35 GMT |
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| EFG |
-kicks tRNA out so another can come into A site
-displaces the A-site tRNA into the P-site
-displaces the P-site tRNA into the E-site |
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mcs5109 Thu, 23 Oct 2008 04:23:59 GMT |
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| Hybrid (intermediate) states |
3’ ends of tRNAs shift into a new location but their anticodon ends are still in their pre-peptidyl transferase position
-"crooked"
-EF-G-GTP then contacts small subunit and kicks tRNA out so another can come in |
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mcs5109 Thu, 23 Oct 2008 04:21:25 GMT |
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| how is peptide bond made? |
-ribosome= ribozyme
-catalyzed by 23S rRNA (of large subunit)
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mcs5109 Thu, 23 Oct 2008 04:21:25 GMT |
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| accomodation |
-tRNA must rotate into P position on large subunit
-incorrect base pairs dissociate |
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mcs5109 Thu, 23 Oct 2008 04:10:37 GMT |
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| How can ribosome prevent wrong aminoacyl tRNA from coming in? |
The fidelity of codon recognition by two adjacent adenine residues in the 16S rRNA in the small subunit. Adenine residues in 16S RNA monitor base pairing between codon and anticodon from minor groove (Fig. 14-31a).
GTPase activity of EF-Tu (Fig. 14-31b).
tRNA accommodation: Only correctly base-paired aminoacyl-tRNAs remain associated with the ribosome as they rotate into the correct position for peptide bond formation (Fig. 14-31c).
2. GTPase activity of EF-Tu
3. accomodation |
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mcs5109 Thu, 23 Oct 2008 04:10:37 GMT |
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| factor binding center |
-domain on large subunit of ribosome
-enhances EF-Tu GTPase activity |
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mcs5109 Thu, 23 Oct 2008 04:10:37 GMT |
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| EF-tu |
-charged tRNA binds to EF-Tu (w/ GTP) to cover aa
-EF-Tu can only bind to tRNA when bound to ATP
-EF-Tu only interacts with the factor binding center after the tRNA is loaded into the A site and a correct codon-anticodon match is made |
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mcs5109 Thu, 23 Oct 2008 04:10:37 GMT |
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| is elongation highly conserved b/w pros and euks? |
yes |
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mcs5109 Thu, 23 Oct 2008 03:51:36 GMT |
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| elongation factors |
-2
-use GTP
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mcs5109 Thu, 23 Oct 2008 03:51:36 GMT |
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| 3 key steps in translation elongation |
1. aminoacyl-tRNA binds to A-site
2. peptide bonds formation
3. translocation from A to P site |
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mcs5109 Thu, 23 Oct 2008 03:51:36 GMT |
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