Translation (general) Flashcards

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1
Q

anti-codon

codon

A

tRNA with AA

mRNA template

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2
Q

rRNA

A

ribosomal RNA has enzymatic activity

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3
Q

what attaches tRNA to its AA

A

amino-acyl tRNA synthetase

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4
Q

rRNA structure

A
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

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5
Q

binding sites in ribosome for tRNA

A

A - acceptor site of incoming aa-tRNA
P - peptidyl site, holds peptidyl tRNA
E - exit site, doesn’t interact with mRNA

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6
Q

all tRNAs..

A

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

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7
Q

tRNA charging by aa-tRNA synthetase

A

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

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8
Q

aminoacyl-tRNA synthetases

A

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

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9
Q

acceptor stem

A

between T loop and 3’ CCA end of tRNA

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10
Q

how is tRNA recognised by their cognate sythetase

A

by identity elements on tRNA at anticodon site but also at G10:C25 base pair region

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11
Q

proofreading of AA attachment to tRNA

A

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)

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12
Q

aminoacyl-AMP

A

intermediate in synthesis of aa-tRNA

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13
Q

why is a flexible CCA arm crucial?

A

because tRNA can move the AA from activation site to the editing site

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14
Q

puromycin

A

resembles aa of aa-tRNA so enters A site so premature chain termination

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15
Q

differences in eukaryotic and prokaryotic translation

A

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

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