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Lecture 10 and 11 Translation and Control
Terms in this set (76)
What are polysomes?
When there are multiple ribsomes on a mRNA chain that start to make the protein.
What does the central dogma state?
That once infomration has passed into proteion it cnanot get out again the transfer of information from nucleic acid, or from nucleic acid to protion may be possible, but transfer from ptotein to protein or from protein to nucleic acid is impossible
What happens to transcription and translation in bacteria?
There are coupled togeth
What are the STOP codons?
UAG, UAA. UGA
What is the START codon?
Why is the genetic code only nearly universal?
there are genetic code variations in mitochondria, mycoplasma, ciliates
What is meant by degenerate codons?
several codons specifiying bacteria amino acids
What is meant by unpunctuated?
non overlapping one after another after anouther
What is a silent mutation?
When a nucleotide is replaced and we get the same exact amino acid out
What is a missense mutation?
When a nucleotide is replaced and a new amino acid is made
What is a nonsense mutation?
When there is an early stop codon and leads to a truncated protein
What is a suppressor mutation?
change the stop codon to something else that elongates the chain
What is a frameshift mutation?
When there is change in teh triple codon reading frame of a mRNAIf there is a multple of 3 then the last AA will just get dropped out. If there is not mutation of 3 then the frameshift is different and the amino acid sequence gets messed up
What is an insertion?
When a nucleotide is added to a sequence causing new amino acids.
What is a deletion?
When a nucleotide sequence is removed from the DNA sequence
What happens to length of proteins in each of these scenarios
Silent - unchanged
Missense - unchanged
Nonsense - Shorter
Suppressor - Longer
Insertion - unkown
Deletion - unknown
What are the eukaryotic ribsome subunits?
80 total 60 and 40 subunites
What are the prokarytoic ribsome subunits?
50 and 30 s with 70s total
What are the ribsome RNAs in eukaytic and prokaryotes?
Eukaroytis 5s, 5.8 s , 28 s in the 60 and 18s in the 40ss
Prokaryotions 50s -> 5s, 23s, 30s ->16s
How many antibiotics in clinical use affect the process of translation?
How many antifungals affect the process of translation?
Few to none
How many antivirals affect the process of translation?
What is pepidyl transferase?
RNA enzyme that forms amino acid peptide bonds between amino acids
How big is the polypeptide exit tunnel?
40-50 aa long
What are the key differences between mRNA in prokaryotes and eukaryotes?
1 5' cap in eukaryotes, 2 3' poly A tail in prokaryotes, 3. polycistronic vs onocistronic 4. splincing occurs in eukaryotes
What makes the eukaryotic mRNA tranlation efficiency better?
functionally circular so that the ribsomes can come back and immediately start to translate once again
What are the proteins on the mRNA?
eIF4E, eIF4G, and polyA binding protein
What does MUPIROCIN inhibit?
Isoleucine-tRNA synthase and sops bacterial creation of isoleucineq
Where does the mRNA pair with tRNA?
at the anticodin region
Which nucleotide on the tRNA provides the amino acid to the growing polypeptide strain?
What is aminoacyl-tRNA synthetase?
This attaches the amino acid to the tRNA
What is pyrophosphatase?
This breaks thte diphosphate bond inorder to couple tthe amino transfer reaction
What are the steps involved in aminoacyl-tRNA?
First there is an activation by reacting with ATP. The amino acid by using aaRS andPPase to adttach the amino acid to the A reagion on the tRNA on the 3' end
Why is aaRS and PPase vital for protein synthesis?
vital for fidelity of protein synthesis and allows proofreading
How can one tRNA code for all the redundancies of the genetic code?
There is a wobble.
What is wobble pairing?
When there is a codon 1, 2, 3 in the mRNA from a 5' to 3' direction then on the tRNA there is a 3,2,1 nucleotide sequcne complementary to the base pairs on the mRNA in a 5' to 3' direction. The last 3rd position on the mRNA has a different nucleotide sequence than when we look at the 1st position on the anticodon going from a 5' to 3' direction
What are the two types of aaRS for Met?
Eukary -Met-tRNA i initiation codon and Met-tRNA for internal met codon or IRES
Prokaryotes - Met-tRNAf and Met-tRNA for internal codon
What are teh initaion enzymes for prokaryootes nad eukaryotes?
Prokaryotes - IF1-3, Eukaryotes - eIF1-5 (multiple)
What are teh elongation enzyme for prokaryotes and eukaryotes?
Prokaryotes - EF-Tu/Ts, EF-G, or (EF1 and EF2), Eukaryotes - eEF1, eEF2
What are the termination enzymes for prokaryotes and eukaryotes?
prokaryotes - RF-1-3, eukaryotes- eRF1, eRF3
What are the two ways ribsomes find their intiations ites in eukaryotes and prokaryotesS?
Eukaryotes - Cap-dependent scanning and internal ribosome entry Prokaryotes - using the shine dalgarno box
What is the shine dalgarno box and what does it have?
It is a sequcne on the 16S rRNA and attaches to the mRNA that is newly synthesized. It is located upstream of the AUG sequence. It tells the ribsome to start translation here
Explain how the IRES initation works?
It works similar to the prokaryotic shine dalgarno sequnce where it attaches to the ribosome and tells the tRNA to start writing
What are teh aminoglycosides?
They are antibiotics like streptomycin, gentamycin, tobramycin, amikacin and cause miscoding during elongation
What does streptomycin stop?
It stops the 30s subunit
What do aminoglycosides do?
They perturb base pairing for prokaryotes
What is the elongation pathway?
First there is a tRNA already in the p-site of the ribosome. Then the aaRS has a tRNA with an aminio acid wheree is then transfered to the amino acid sitting in the psite is not transfered to the a site. Then there is translocation of the tRNA with the new peptide chain over to the p site
What does puromycin imitate?
AA-tRNA as it looks like the tRNA chain and can take up some loose amino acids that come by
Why can't we use puromycin for eukaryotes?
It will kill eukaryotes as it takes up amino acids in eukaroytes as well
What produces diptheria toxin?
corynebacterium diphtheriae (tox+)
What happens to the diphtheria toxin?
It is a protein that is cleaved into two fragments, A and B. B causes the toxin to be internalizeda nd Fragmetn A poisons translation one molecule is ifficient to kill a cell
What does the diphtheria toxin do?
It catalyzes ADP-ribosylation of eEF2 and makes eEF2 + NAD+ to make ADP-ribosyl-eEF2 + nicotinamie + H+
What is the modified histidine residue which ADP-ribose is transferred onto?
diphthamide in eEF2
What antibiotic stops diphteria toxin?
What is Ricin?
It is a protein toxin on casor beans where <1 mg can kill an adult and 1 bean can kill a child. It consists of 2 polyepetide chains.
What are teh two chains of ricin?
B chain binds a cell surface receptor for uptake, A chain depurinates 28S rRNA at a specific A residue
What is termination of the tRNA?
When there is a release protieon which comes and attaches to the mRNA sequence and allows the ribosome to be removed from the mRNA sequence
What is chargine for proteion synthesis and how much ATP is used?
When every new AA is brought into the ribosome. There is an expenditure of 2 ATP
What is energetics of initaion, elongation and termination?
Unwinding and scanning ATP 1
Met-tRNA binding GTP 1
AA-tRNA binding GTP 1
Translocation GTP 1
What is the total energetic of protein synsthenic per AA?
4 ATP with initation terminand termintion going up t o 8
What is the example in which a specific way translation is controlled?
There is a ferrtitin molecule which takes up Fe+ in the cell. This iron is then taken up b ferritin and attacesh to the IRO region, iron response element region. The IRE-BP protein comes in and binds to this IRE on the ferritin molecule and stops the ferritin from working properly. This IRE-BP comes in an attaches to IRE when Fe+2 levels are low inside the cell
What is hereditary hyperferritinemia?
This is a cataract syndome causes by mutations in the IRE as the IRE mtuation in ferritin mRNA cannot bind IRE-BPand the ferritin systehs is de-repressed
Explain the down regulation of the supply of initiaor Met-tRNA via the eIF2 kinases
As the eIF2 is made for intitaiont after it is done with protein synthesis the eiF2 protion would go back and become phosphorylated by kinases this would trap the eIF2 preption and halt inhibition.
What are some eIF2 kinases?
HRI: reticulocyte minus heme, PKR: interfoeron plus virus infection (dsRNA), PERK: ER stress, and GCN2: amino acid starvation
What causes vanishing white matter?
neurological deterioration exacerbated by head trauma and a mutatin in any of the 5 subnstioes if eIF2B
What is the upregulation of eIF4E
In order to upregualte eIF4E w/o a 4E-BP which will be phosphorylated. we would need to add on eIF4A and eIF4G and E together to create protein synthesis. This is done through a kinase cascade.
How is eIF4E downregulated?
There would be an addition of 4E-BP on the eIF4E protein which would cause the eIF4E to inhibition intitaion
What was is the eIF4E part of?
part of a complex required for scanning and its function is cireaed by phosphorylation of 4E-BP and eIF4E itself
Call aminoglycosides targets 30S and inhibits inintiation cause misreading
Class tetracylcin target 30s and inhibitions binding of AA-tRNato the A-site
Inhibit peptidyl transferase and is 50S
Macroclides 50s and inhibit translocation
50s and 60s and premature release of nascent polypeptide
Explain Diphtheria toxin
60S inhibits AA tyna site
60 S inhiits binding of AA-tRNA to A site
What are differences between prpokaryotes and eukaroyrs?
Prokaryotes no nucleus, transctoio nad tralsion is coupled, polycistronic, ribosomes 70S (50s and 30S, fMet-tRNA there is a shine-dalgarno mediated internal initiation intiaitonaactors are 3 antibiotsn sensiint
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