Riboswitches
What subunit does the prokaryotic ribosome consist of?
30S subunit 50S subunit forms 70S subunit
What subunits do the eukaryotic ribosome consist of?
40S subunit 60S subunit forms 80S subunit
What is the mechanism of translation in eukaryotes?
All of the chemicals start with eIFx (with x being a number or letter) 1. 40S subunit binds to 1/1a/13 2. Ternary complex consists of 2/GTP/tRNA18 3. Both of them bind together forming Pre-initiation complex or 43S 4. 4E binds to 5'cap of mRNA 5. 4E interacts with 4G/4A/4B forming 4F complex 6. 4G interacts with 3, bringing the complexes together 7. The complex scans the mRNA for AUG start codon 8. GTP hydrolysis occurs, leaving only the 40S subunit and 1A which binds to 60S subunit and 5 9. Translation occurs via closed-loop model
Give an example of a metabolite riboswitch
III S-adenosyl methionine (SAM) Initiates metK gene
What is the closed-loop model?
Poly(A) tail enhances translation efficiency through interacting with PolyA binding protein, creating a spiral eIF4G binds to PolyA binding protein, increasing subunit efficiency.
Give an example of a temperature-mediated riboswitch
PrfA Transcription of virulence genes in Listeria monocytogenes. Active at 37C, silent at 30C
How is eukaryotic translation regulated
Reduces the amount of ternary complex available Blocks formation of 48S complex via 4E regulation
How does translation in prokaryotes occur?
Ribosome is recruited to the shine-dalgarno sequence 16S rRNA consists of UUCCUCC anti-shine dalgarno sequence Translation is initiated
What are riboswitches?
Riboswitches are specialised domains within certain mRNAs that function as sensors for diverse signals such as temperature, amino acids, metal ions and salt concentrations.
RNAP 2 will bind to the shine-dalgarno sequence in prokaryotes as well as its start codon. If a metabolite binds, what happens?
The metabolite will induce a change in structure which will make the SD and start codon inaccessible by RNAP 2
How are riboswitches regulated?
Transcriptional attenuation Regulation of translation initiation (Assembly of Shine-Dalgarno sequence)