Lecture 6-Translation (Rosenthal) Flashcards
How many aa’s are there for prokaryotes? Eukaryotes?
- 20
- 20
How many tRNAs are there for prokaryotes? Eukaryotes?
- 20+
- 20+
The aa code is degenerate meaning _____.
There are multiple codons for each aa
Explain what happens when each respective nucleotide is in the wobble position of the codon.
- A/C: there is only 1 tRNA that can read it, they cannot pair with anything else
- G/U: 2 tRNAs can read these: G can bp w/C or U; U can bp with A or G
- I: 3 different codons can recognize because it can bp with A, U, C
How many tRNAs total are there for the 20aas including the starter Met?
32
Activation of tRNAs requires what 4 things?
- tRNAs
- aminoacyl tRNA synthetase (and therefore ATP)
- specific aa for tRNA
Which site on the aminoacyl tRNA synthetase is responsible for the proofreading activity?
Hydrolytic site
CMT1
CMT is one of the most common inherited nerve disorders: mutation in an aminoacyl-tRNA synthetase resulting in polyneuropathies
CMT2. Type 2D?
mutation in an aminoacyl-tRNA synthetase resulting in axonal polyneuropathies.
- Type 2D: glycyl-tRNA synthetase gene (GARS)
intermediate CMT. Type C?
mutation in an aminoacyl-tRNA synthetase
- Type C: tyrosyl-tRNA synthetase gene mutation (YARS) causing localization of aminoacyl tRNA synthetase in granules of neuronal cells
What do mutations in RPS19 and/or RPS24 result in?
- RPS19 is required for maturation of the 40S ribosomal subunit
- RPS19 and 24 might be involved in binding eIF2
- Mutations result in impairment of translation initiation; Diamond Blackfan anemia (DBA)
transformylase
the enzyme in prokaryotes that adds the formyl group onto the initiator Met–designated fMet-tRNA^fMet
How is eukaryotic initiator tRNA different from the rest?
The Met is not different from any other Met tRNAs, but when it is written out it is denoted: Met-tRNA^iMet
Shine-Dalgarno sequence
- an A/G (purine)-rich sequence upstream of prokaryotic mRNA that (along with the TpsiC arm and codon-anticodon interaction) keeps the ribosomal subunit locked in place
VWM (Vanishing White Matter)
- mutations in the eIF2B subunits resulting in
- ataxia
- CNS hypomethylation
Wolcott-Rallison Syndrome
- mutation in PERK and therefore difficulties shutting down protein synthesis:
- childhood diabetes mellitus (highest expression of PERK in beta cells) and therefore there may be difficulties shutting down insulin production beyond the capacity of the ER (and UPR?) and beta cell apoptosis
NOTE: - mental retardation
- hypothyroidism
- dysfunctional liver, kidney, pancreas
Subsequent tRNAs that are added to the peptide chain are attached to ______ which helps them enter the ribosome
Prokaryotes: Tu-GTP
Eukaryotes: eEF1-alpha
After 2nd through last aas are added to the peptide chain, how are the EF-Tu-GTP/eEIFalpha regenerated for the next tRNA entry?
Prokaryotes: Tu-Ts
Eukaryotes: eEF1-beta-gamma
Which non-RF releasing factors are involved in ribosome release (prokaryotes)?
- EF-G (helps the ribosome translocate)
- RRF (ribosome recycling factor)
- IF-3: releases large subunit and therefore everything else
Which RFs are involved in termination and what do each of them recognize?
Prokaryotes:
- RF1: UAA and UAG
- RF2: UAA and UGA
- RF3: helps RF1 and RF2 work, also helps in ribosome dissociation (requires ATP)
Eukaryotes:
- RF1: UAA, UAG, UGA
- RF3: causes release of ribosome and hydrolyzes peptide
What are mutations in the eEFs and what disease(s) do they cause?
- no known mutations in these
What are the mutations in eRF3?
- GGC (Lys) expansion in gastric cancer
- most common gives 10 gly’s and 12 gly form has been only seen in cancer patients
- causes a 20-fold increase in risk of gastric cancer
what causes mRNA misreading/blocks inititation?
- streptomycin (changes 30S rRNA)
What drugs block peptidyl transferases and therefore elongation?
Eukaryotes:
- cycloheximide: interferes with EF-G (a prokaryotic protein?)
Prokaryotes:
- chloramphenicol: inhibits peptide bond formation; last resort since it also works on mitochondria
