CSF (Protein Synthesis) Flashcards
Transcription (Initiation)
In the promotor, there’s a TATA box and start point. Transcription factors and TATA box binding protein bind to DNA. RNA Polymerase 2 binds.
Transcription (Elongation)
RNA nucleotides added to 3’ end of template strand. Phosphodiester bond.
Transcription (Termination)
Transcription of the Polyadenylation signal (AAUAAA) then nuclear enzymes release mRNA.
mRNA Processing
Capping: a modified guanine nucleotide is added to 5’ end.
Tailing: Poly-A tail on 3’ end.
Splicing: Introns removed from transcript.
UTR: untranslated regions at 3’ and 5’ ends.
What does capping and tailing do?
Facilitate export, confer stability, facilitate ribosome binding once in cytoplasm.
Translation (Elongation)
Codon recognition, peptide bond formation (large subunit catalyses), translocation (tRNAs move again). GTP.
What happens to empty tRNAs after translation?
They are reloaded in cytoplasm using aminoacyl-tRNA synthetases.
Translation (Termination)
mRNA stop codon one the A site is bound by a release factor. The bond between P-site tRNA and last amino is hydrolysed, releasing chain. Hydrolysis of 2GTP.
Primary Structure
N terminus = amino end (like 5’)
C terminus = carboxyl end (like 3’)
Covalent bonds btwn amino acids.
6 steps of protein processing and sorting.
- Polypeptide synthesis begins.
- SRP binds to signal peptide.
- SRP binds to receptor protein.
- SRP detaches, poly.p. resumes.
- Signal-cleaving enzyme cuts off signal peptide.
- Completed poly.p. folds. A secretory protein (eg.insulin) is soluabilized in lumen while a membrane protein remains anchored to mem.
Both then go to Golgi for further maturation.
Post-translational modifications
Phosphorylation (in golgi or cytosol).
Can confer activity or ability to interact with other molecules or direct to particular locations.
