6 - Protein translation and post-translational modification Flashcards
What direction is the protein synthesised in?
N ——> C direction
Which end of the tRNA molecule if the amino acid attached to?
3’ end
Describe the pre initiation complex
eIF-2 binds to Met-tRNA and a molecule of GTP
The other side of the Met-tRNA is bound 40S subunit
NOTE: Only initiator Met-tRNA can bind to the 40S subunit alone. All other tRNA of other amino acids can only bind to the fully formed ribosome
The 40S subunit is primarily involved in tRNA binding and mRNA recognition
Where is the pre initiation complex formed?
in the cytoplasm
Which enzyme catalysis the formation of the peptide bind between 2 amino acids?
peptide transferase
What is the role pf elongation factors?
promote the movement of the ribosome along the mRNA using energy from GTP
enhance the accuracy and efficiency of translation by providing pauses (e.g. ATP hydrolysis) that allow incorrect base pairs to dissociate
What is the role of peptide transferase in the termination step of translation?
catalyses the transfer of the completed polypeptide chain to water and leases it from the ribosome
What is the name of the proteins that travel from the cytoplasm to the compartments (organelles)?
Which organelle had a critical role in this?`
secretary and transmembrane proteins
RER
What do proteins that are destined to be secretory of transmembrane have? Where is it located?
a signal sequence at the N-terminus of the polypeptide
NOTE: it is rich in hydrophobic amino acids
What happens to the proteins once it has entered the ER?
the signal sequence is cleaved by signal peptidases and degraded.
The protein os then folded.
Gove examples of post-translational modifications?
- disulphide bond formation
- proteolytic cleavage
- glycosylation
- phosphorylation
- prenylation and acylation
- hydroxylation
Where is insulin translated?
on membrane-bound ribosomes on ER
