Translation - DNA to RNA to protein Flashcards

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1
Q

Initiation of translation in prokaryotic - Shine-Dalgarno / Ribosome Binding Site

A
  • A sequence upstream from the mRNA’s start codon that tells the ribosome where to start translating
  • Binds the 16S rRNA
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2
Q

Components required for prokaryotic translation

A
  • Ribosomes
  • mRNA
  • fMet-tRNA(fmet)
  • initiation factors (IFs)
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3
Q

What is needed for the assembly of the translation apparatus?

A

One molecule of GTP

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4
Q

How translation is intiated in prokaryotes

A
  • Initiating tRNA (fMet-tRNA(fMet)), small ribosomal subunit + mRNA form a complex
  • This is followed by binding of large ribosomal subunit
  • Then ready for elongation phase
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5
Q

Initiation of translation in eukaryotic - eIF

A
  • ‘Eukaryotic Initiation Factors’ help the ribosome bind to the 5’-Cap and find the first AUG codon (start)
  • Don’t contain a Shine-Dalgarno sequence or equivalent
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6
Q

How translation is initiated in eukaryotes

A
  • Initiating tRNA (Met-tRNA(Met), small ribosomal subunit and the mRNA form a complex
  • Then large ribosomal subunit binds
  • Ready for elongation phase
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7
Q

Components required for eukaryotes

A
  • Ribosome
    -mRNA
  • Initiation Factors (eIFs)
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8
Q

What is needed for the assembly of translation apparatus in eukaryotes?

A

1 ATP + 1 GTP

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9
Q

The P (peptidyl) Site - Step 1

A
  • At beginning of each cycle, the growing peptide chain is attached to the tRNA
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10
Q

The A (aminoacyl) Site - Step 2

A
  • Incoming aminoacyl-tRNA is delivered by an elongation factor (EF-Tu/eEF1alpha) to here - GTP needed
  • A decoding centre in A make sure the right aa-tRNA is delivered
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11
Q

How the peptide bond is formed - Step 3

A
  • Growing chain is transferred from t-RNA in P site
  • To the amino group of the AA is carried by the tRNA in the A site
  • Peptide bond is formed
  • The peptidyl transfer reaction is catalysed by peptidyltransferase activity of ribosome
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12
Q

Ribosome moves along the mRNA - Step 4

A
  • This translocation step requires an elongation factor (EG-G/eEF2) and GTP
  • tRNA carrying the growing peptide –> P site
  • Uncharged tRNA –> Exit site (E)
  • A site is now occupied by next codon on mRNA
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13
Q

Where the uncharged tRNA goes + how the cycle continues - Step 5

A
  • Leaves the ribosome and the next aminoacyl-tRNA is delivered to the A site by EF-Tu
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14
Q

Termination of translation

A
  • When the stop codon occupies the A site, no aminoacyl-tRNA can bind to A site
  • Release factors bind to A site to release new protein from ribosome
  • Factors (RRF, EF-G, IF3) lead to release of uncharged tRNAs & large + small ribosomal subunits dissociate
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