BIO SCI 98 Lecture Notes - Lecture 6: Peptidyl Transferase, World Federation Of Trade Unions, Transfer Rna
19 Jun 2018
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Necessary = you need it to carry out that function
- How to test: remove it and see if function is retained
- Ex: deleting a gene, removing a factor
Sufficient = you can get function with only that thing
- How to test = add item in isolation and see if function can occur
- Ex = in vitro reaction where you add only one component of a complex, removing all
other factors except one
Translation Elongation Overview
3 steps:
1) aminoacyl-tRNA enters ribosome
2) Peptide bond forms
3) Ribosome shifts to next codon
Extremely similar between bacteria and eukaryotes
- We will only cover bacterial
Elongation Step 1 - incoming tRNA
Step 1
a) EF-Tu escorts new aminoacyl-tRNA into A site of ribosome
i) EF-Tu is bound by GTP
ii) EF-Tu protects aminoacyl-tRNA from hydrolysis
b) Once tRNA is in A site, EF-Tu GTP is hydrolyzed to GDP and EF-Tu leaves
i) EF-Tu-GDP is recycles and GTP regenerated by EF-Ts
c) Accomodation - correct tRNA base-pairing brings its amino acid in close proximity to
polypeptide
i) Proofreading occurs here by ribosome to ensure correct tRNA is in A site (reject
or accommodate)
Fun fact = EF-Tu is most abundant protein in E. Coli cell
find more resources at oneclass.com
find more resources at oneclass.com
Short
version
EF-Tu escorts new AA-tRNA into A site, GTP hydrolysis helps position tRNA correctly
(accommodation) and kicks out EF-Tu
Elongation Step 2 - Peptidyl Transferase Reaction
- Catalyzed by 23S rRNA in large subunit, Mg2+ is involved
- Nucleophilic attack of amino group (A site) to carbonyl carbon ester bond (P site)
- 2 results
1) Peptide bond forms between amino group of A site amino acid and carboxyl
group of P site amino acid
2) aminoacyl-tRNA bond of P site is severed, so A site's tRNA is where the growing
polypeptide is now linked
- Powered by releasing energy in aminoacyl-tRNA bond
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Necessary = you need it to carry out that function. How to test: remove it and see if function is retained. Ex: deleting a gene, removing a factor. Sufficient = you can get function with only that thing. How to test = add item in isolation and see if function can occur. Ex = in vitro reaction where you add only one component of a complex, removing all other factors except one. Step 1: ef-tu escorts new aminoacyl-trna into a site of ribosome i) ii) Ef-tu protects aminoacyl-trna from hydrolysis: once trna is in a site, ef-tu gtp is hydrolyzed to gdp and ef-tu leaves i) Ef-tu-gdp is recycles and gtp regenerated by ef-ts: accomodation - correct trna base-pairing brings its amino acid in close proximity to polypeptide i) Proofreading occurs here by ribosome to ensure correct trna is in a site (reject or accommodate) Fun fact = ef-tu is most abundant protein in e. coli cell.
