Translation (general) Flashcards
anti-codon
codon
tRNA with AA
mRNA template
rRNA
ribosomal RNA has enzymatic activity
what attaches tRNA to its AA
amino-acyl tRNA synthetase
rRNA structure
conserved regions (stems) in all species and mutations are lethal variable regions (balloons) can tolerate mutations
conservation of structure by compensating base changes so point mutation happens but 2nd point mutation restores base pairing
binding sites in ribosome for tRNA
A - acceptor site of incoming aa-tRNA
P - peptidyl site, holds peptidyl tRNA
E - exit site, doesn’t interact with mRNA
all tRNAs..
have same structure (described in prokaryotic translation cards)
interact with elongation factor apart from initiator tRNA
bind to A site in ribosome
CCA terminal addition
invariant modifications to bases
tRNA charging by aa-tRNA synthetase
amino acid and ATP bind to synthetase and AMP covalent binding activates AA and pyrophosphate is released
tRNA binds to synthetase so AA covalently bonds to tRNA and AMP is released and charged tRNA is released
each synthetase recognise single AA and all tRNAs charged by it
aminoacyl-tRNA synthetases
charges tRNA with AA
2 groups each with 10 enzymes
class I: contact tRNA at minor groove of acceptor stem and anticodon, N-terminal a-b-a-b catalytic sites, further classification by subunits structure
class II: contact tRNA at major groove of acceptor stem and anticodon, central b surrounded by a catalytic sites
classes recognise diff faces of tRNA and CCA adopt diff conformations
acceptor stem
between T loop and 3’ CCA end of tRNA
how is tRNA recognised by their cognate sythetase
by identity elements on tRNA at anticodon site but also at G10:C25 base pair region
proofreading of AA attachment to tRNA
double sieve so 2 stages
1) hydrolysis of ester bond of aminoacyl-AMP intermediate if incorrect AA attached
2) hydrolysis of ester bond of miss-matched aminoacyl-tRNA (tRNA with AA attached)
aminoacyl-AMP
intermediate in synthesis of aa-tRNA
why is a flexible CCA arm crucial?
because tRNA can move the AA from activation site to the editing site
puromycin
resembles aa of aa-tRNA so enters A site so premature chain termination
differences in eukaryotic and prokaryotic translation
diff ways of signalling, initiation/termination regions
euk is monocistronic so 1 gene encoded with cap and poly-A tail
prok is polycistronic with more than 1 gene on an mRMA with related activities with RBS
tRNA fmet in prokaryotes - Met residues attached and formylated, recognised by start signal AUG and GUG
tRNA mmet in eukaryotes - Met only attached and NOT formylated and recognise AUG only and won’t react with start signal