BIOL 308 > Translation > Flashcards

Translation Flashcards

(56 cards)

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1
Q

what is translation ?

A

the processing of mRNA into a polypeptide/protein mediated by ribosomes

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2
Q

what does mRNA do?

A

it carries genetic information from DNA in the form of codons

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3
Q

what does tRNA do?

A

translated mRNA code, each AA has its own tRNA

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4
Q

how does tRNA bind ?

A

binds due to codon-anticodon complementarity

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5
Q

what does rRNA do in translation ?

A

associates with proteins to form ribosomes which catalyze the assembly of polypeptide chains

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6
Q

how many nucleotide does tRNA have ?

A

73- 93 nucleotides

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7
Q

what synthesizes tRNA and which promoters ?

A

RNAP III, type 2 promoters

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8
Q

what are 2 key elements on a tRNA?

A
  1. Anti Codon Loop
  2. AA acceptor arm
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9
Q

what are 5 modifications occur to tRNA ?

A
  1. Dihydrouridine
  2. inosine
  3. Thymidine
  4. pseudouridine
  5. Methyl group
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10
Q

when are introns present in tRNA?

A

pre-modification

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11
Q

how is splicing initiated in tRNA?

A

splicing is initiated by recognition of common secondary structure within tRNA as there is no consensus sequence

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12
Q

what is the 5 step tRNA splicing ?

A
  1. 5’ leader sequence removed by RNase P
  2. 3’ trailer sequence is removed by endonuclease and exonuclease
  3. CCA added to 3’ end by nucleotidyl transferase
  4. intron spliced out by multiple enzymes
  5. Additional Modifications ( 5 Mods)
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13
Q

what is the difference between RNase P in ribozyme in bacterial and eukaryotic ?

A

bacterial is a ribozyme
eukaryotic is a nucleolar RNP

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14
Q

what are the two functions of tRNA ?

A
  1. Link to an specific AA
  2. Recognize a Codon in mRNA to add AA
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15
Q

how many enzymes recognize a tRNA and how many bind

A

20 enzymes and 1 can only bind

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16
Q

how can a tRNA be charged ?

A

by the transfer of aminoacyl group from the enzyme complex to tRNA which activates AA residue

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17
Q

what is the part of the tRNA that interacts with the codon in mRNA?

A

anticodon which forms complementary bases with the mRNA codon

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18
Q

what part of the tRNA accept AA as the acceptor stem ?

A

CCA at the 3’ end

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19
Q

what does aminoacyl- tRNA synthetase (ARS) do?

A

it catalyzes the attachment of AA to a free 2’ or 3’ hydroxyl on ribose of the adenosine (AMP) in the 3’ end of tRNA

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20
Q

what does the ribosome recognize?

A

tRNA

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21
Q

what is the 2 step method for tRNA. charging

A
  1. adenylylation of AA (using ATP)
  2. transfer of the adenylated AA to 2’ or 3’ hydroxy on ribose of AMP
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22
Q

what is non standard base pairing

A

where a single tRNA is able to recognize more than one codon for an AA in wobble position

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23
Q

what is the wobble position for mRNA and tRNA ?

Study These Flashcards
A

in mRNA the wobble postion is in the 3rd spot
in tRNA the position in the in 1st spot

24
Q

what is a ribosome?

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A

a complex of rRNAs an protein that direct elongation of a polypeptide

25
what is Svedberg units ?
in relation to ribosomes it is a measure of the velocity of particles when centrifuged under constant conditions; dependant on size.
26
what is the prokaryote ribosomes svedburg unit overall and what are there 2 subunits svedburg units
70s ribosome overall 1. 50s 2. 30s
27
what is the eukaryotes ribosomes svedburg unit overall and what are there 2 subunits svedburg units
80s ribosome overall (larger than pro) 1. 60s 2. 40s
28
in terms of rRNA for prok and euk what is common and what is different
for pro they have 16s and for euk they have 18s but both for 5s rRNA
29
what are the 3 trna binding site in ribosomes? (APE)
1. Aminoacyl site: where aminoacylated tRNA bind (charged tRNA) 2. Peptidyl site: where polypeptide grows 3. Exit site : empty tRNA site ( no charged tRNA
30
what starts protein synthesis?
the initiator tRNA positioned at the start codon AUG
31
what are the 2 types of methionine tRNA pro and euk have ?
tRNAmet- for methionine at internal codons tRNAi met- solely for initiation
32
what is needed to specifically initiation translation in bacteria and where?
the shine dalgarno which is a conserved sequences and the ribosome binding site that base pairs at 3' end of 16s rRNA in 30s subunit
33
compared to Euk, how many RBS does does prokaryotes have and what does it allow?
they can have multiple RBS sites due to polycistronic mRNAs that lead to different protein being made at the same time.
34
How is the prokaryote ribosome subunit formed in 8 steps ?
1. IF3 binds to 30s small subunit 2. IF1 binds 3, the IF2 complex with GTP and binds to 30s 4. mRNA binds to small subunit via shine dalgarno seq 5. initiator tRNa goes to p site (above is 30s complex unit) 6. 50s subunit BINDS 7. IF2 is released and GTP hydrolysis 8. 70s initiation complex is ready(without IF2)
35
what is IF1 , IF2 , IF3 role when binded ?
IF1- prevents binding of tRNA to A site IF2- gtpase IF3- prevention of 50s subunit binding
36
How is the eukaryote ribosome subunit formed in 8 steps
1. 40s subunit complexes with eIF3 and eIFA 2. ternary complex forms: initiator tRNA, eIF2 and GTP 3. ternary complex binds to 40s complex and eIF1 binds (43s preinitiation complex 4. mRNA binds to the 43s complex via 5' methyl cap 5. 43s scans mRNA to find kozak sequence using ATP 6. initiation factor displaces now (40s initiation complex formed) 7. 60s subunit binds with GTP Hydrolysis 8. 80s initiation complex is formed
37
what is eIF3 and eIF1A used for ?
preventing the 60s subunit from binding
38
what are the 3 ways of controlling translation ?
1. Phosphorylation 2. multiple AUG codons 3. IRES ( Internal Ribosome Entry Site) these can all act together
39
what are the 4 reason eukaryotes need control on translation ?
1. Change in nutrients 2. change in energy availability 3. response to stress 4. hormones and growth
40
what can impair scanning efficiency for start codon in mRNA for translation?
inhibitory secondary structures in the 5' untranslated region
41
what is the kozak sequence
a sequence in the euk that contains the start codon AUG
42
What 3 thing happens when eIF2 IS down regulated for translation control?
it phosphorylated 1. low AA levels that accumulate uncharged tRNAs (no translation) 2. activates protein kinase 3. eIF2 cant be recycled as usual
43
what happens in kozak sequence is weak?
scanning of ribosomal unit for AUG codon is leaky with move to second or third AUG and differ the N terminus in proteins
44
what is the AUG/UGA codon used for
it is a short open reading frame between the 5' end and the beginning of the main coding sequence (upsteam ORF) that stalls and down regulates that translation of a downstream gene
45
what does IRES(internal ribosome entry sites) ? do for translation control
it enables methyl cap independent translation by bypassing the requirement from eIF4E (which binds cap) and eIF4G (binds PABP) factors
46
why is IRES are important?
allow for regulation of balance between cell apoptosis & cell division during virus infection and stress conditions when cap dependant is decreased also location AUG codon
47
what is the 5 step for prokaryote elongation?
1. Ternary complex: Amino acyl-trNA (charged with AA) binds to EF-Tu and GTP and binds to A site and pairs with codon on mRNA 2. Peptide Bond forms between previous AA and new AA 3. amino-acyl tRNA (charged) becomes peptidyl tRNA at A-site 4. unloaded tRNA is at P-site 5. Ribosome shifts to 3' to get another codon in A site which is catalyzed by EFG (PRO) using GTP
48
when ribosome shift where are the tRNA now located
peptidyl tRNA is in P site the empty tRNA is at E site A site is empty
49
what is the 3 step eukaryotic elongation
1. Amino-acyl tRNA, eEF1a, eEF1b and GTP binds to A site 2. Peptide bond forms and peptidyl-tRNA in A site and unloaded tRNA is at P site 3. ribosome shift 3' (translocation) by eEF2 using GTP
50
what occurs in the reaction for the peptide bond ?
amide group attack carboxylic acid group which form the peptide bond via rRNAs catalytic unit
51
what is peptidyl transferase?
it catalyses the transfer of the growing peptide chain to the incoming activated amino acid and makes a peptide bond
52
what recognizes the stop codons?
the stop codons are recognized by release factors that are GTP hydrolyzed , trna is not present
53
what are the two function of peptidyltransferase?
1. peptide bond formation, elongation 2. nascent peptide release, termination
54
what is the 3 factors required for translation termination?
1. no charged tRNA 2. Hydrolysis of ester bond linking polypeptide at p site 3. nascent peptide release
55
what are 2 difference in regards to bacteria for the initiation of translatio n ?
1. f-met is attached instead of regular met 2. Alternate starts AUG & GUG must be recognized by bacteria
56
what is an antiparallel interaction ?
the interaction btw codon (5'-3') and anticodon ( 3' -5')
BIOL 308
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