Study BMB 400 Chap 14 Translation Elongation Flash Cards

 
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BMB 400 Chap 14 Translation Elongation

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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)
EF-Ts
-GTP exchange factor for EF-Tu
EF-Tu and GTP
-elongation factor EF-Ts acts as a GTP exchange factor for EF-Tu
EF-G and GTP
-EF-G: GDP has a low affinity for EF-G
-rapidly released after hydrolysis
structures
structure of EF-G-GDP is very similar to that of EF-Tu-GTP-tRNA complex
E site
-no codon:anticodon interaction
-no affinity, so tRNA released
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
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
how is peptide bond made?
-ribosome= ribozyme
-catalyzed by 23S rRNA (of large subunit)
-
accomodation
-tRNA must rotate into P position on large subunit
-incorrect base pairs dissociate
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
factor binding center
-domain on large subunit of ribosome
-enhances EF-Tu GTPase activity
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
is elongation highly conserved b/w pros and euks?
yes
elongation factors
-2
-use GTP
-
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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