Protein translation and post-translational modification Flashcards Preview

MCD - Nucleic Acids and Gene Expression > Protein translation and post-translational modification > Flashcards

Flashcards in Protein translation and post-translational modification Deck (14):
1

How mRNA sequence are read

AAs read in triplets
Each triplet is a frame
Translation starts at first start codon and continues in frame
Stops at first in-frame stop codon

2

Start codon sequence

AUG

3

Stop codon sequences

UAA
UAG
UGA

4

Location of translation and RNA involved

Occurs in ribosomes
tRNA main component

5

How is the fidelity of the genetic code maintained?

Aminoacyl tRNA synthetases
- AA gets stuck onto correct tRNA by synthesise
- One aminoacyl tRNA per amino acid
- Hydrolyses incorrect amino acid-tRNA pairings and inserts correct one

6

Process of translation

INITIATION
- Dissociation of ribosome subunits
- Assembly of pre-initiation complex
- Binding of mRNA to pre-initiation complex
- Binding of 60s subunit
ELONGATION
- Binding of new tRNA carries AA to A site
- Peptide bond is formed between the 2 amino acids via peptide transferase
- Translocation of tRNA to P site and dissociation of first tRNA
- Cycle repeats for each new AA added to the sequence
TERMINATION
- Stop codon recognised by release factors
- Peptidyl transferase release peptide chain
- Dissociation of ribosomes and release factors

7

Mechanisms of antibiotic protein inhibition

- Translational machinery is complex and easily disrupted, common target for antibiotics
- Antibiotics exploit differences between prokaryotic and eukaryotic ribosomes and translation factors
- Antibiotics selectively inhibit prokaryotes

8

Examples of antibiotics that inhibit protein synthesis

- Streptomycin, inhibits initiation
- Tetracycline, inhibits aa-tRNA binding
- Erythromycin, inhibits translocation
- Chloramphenicol, inhibits peptidyl transferase
- Puromycin, terminates elongation prematurely

9

Method of identifying proteins destined to be secretory or transmembrane

These proteins have a special 'signal sequence'.
This sequence is recognised by a 'signal recognition particle'.

10

Process and steps of pathway for newly-synthesised protein to enter secretory pathway

- Recognition of signal sequence by signal recognition particle, halts translation
- Binding of SRP to receptor on the surface of RER, translation resumes
- Translocation of growing polypeptide into RER lumen
- Transmembrane proteins have one or more extra hydrophobic sequences which hold them in membrane
- Cleavage of signal sequence in protein, protein folds inside ER

11

Ways newly-synthesised proteins can be post-translationally modified

- Disulphide bond formation
- Proteolytic cleavage
- Glycosylation
- Phosphorylation
- Prenylation, acylation
- Hydroxylation

12

Explain glycosylation

Addition of carbohydrate to a fully synthesised protein

13

Explain phosphorylation

Addition of phosphate to a fully synthesised protein

14

Explain prenylation and acylation

Two types of addition of lipid groups to a fully synthesised protein