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19 Flashcards

(58 cards)

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1
Q

four sub steps in elongation

A
  1. decoding
  2. accomodation
  3. peptide bond formation
  4. translocation
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2
Q

decoding

A

charged tRNA enters the ribosome
base paiting between the mRNA and the tRNA anticodon
release of EFTu and eEFIA

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3
Q

accomodation

A

movement of aminoacid end of tRNA into the peptidyl transferase centre

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4
Q

translocation

A

role of EFG and eEF2

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5
Q

how many elongation factors for bateria adn euk

A

4 for both

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6
Q

elongation factos for bacteria

A

EFTu
EFTs
EFG
EFP

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7
Q

elongation factos for euk

A

eEF1A
eEFIBa
eEF2
eIF5A

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8
Q

functional equivalent for EFTu

A

eEF1A

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9
Q

fucntional equivalent for EFTs

A

eEF1Ba

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10
Q

functional equivalent for EFG

A

eEF2

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11
Q

functional equivalent for EFP

A

eIF5A

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12
Q

what can enter the A site in bacterai and euk

A

EFTu/eEF1A
EFG/eEF2
eRF3
Hbs1
RF1, RF3

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13
Q

WHAT DOES eEF1A do

A

delivers aatRNA to sense codons

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14
Q

what does eRF3 do

A

delivers eRF1 to stop codons

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15
Q

what does hbs1 do

A

delivers pelota to stalled ribosomes (no codons)

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16
Q

how does EFTu and EFG bind to ribosome faster than other things

A

bc the L12 ctds reach into soln to catch translation factos and hand them over to the ribosomal factor binding site

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17
Q

what happens during deconding

A

aatRNA is delivered by EFTu and eEF1A - not selected by ribosome- depends on matching

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18
Q

single mismatch

A

near cognate

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19
Q

non cognate

A

two or more mismatches

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20
Q

what does the cognate tRNA anticodon match with

A

forms a double strand helix with the mRNA codon

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21
Q

what facts about the double helix formed between the codon and the cognate tRNA

A

it is short and relatively unstable
must allwo for wobble
near cognate might be just as stable

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22
Q

how do we know that the correct tRNA is matched

A

like a trigger loop
-conserved nucleotides in 16RNA respond to formation of double helix- they change conformation and interact with the minor groove fo the codon anticodon helix

they help stabilize the A siete tRNA via hydrogen bonding providing tolerance at position 3

same for eukaryotes but in the 18s decoding centre

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23
Q

what happnes when we decide that the codon anticodon interaction is good

A

confromational changes in the ribosome
L7/12 stalk acts as a GAP for EFTu and eEF1A

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24
Q

what are two latent GTPases for this section

Study These Flashcards
A

EFTu and eEF1A

25
what does GAP activating GTPase of EFTu and eEF1A lead to
them releasing the aatRNA and accomodation proceeds
26
what happnes if codon anticodon interactin is not good
EFTu and eEF1A normally dissociate away but it depends on how stable they are -if stable might GTP hdyrolyze first but aatRNA might diffuse away before accomodation starts -or might diffuse away before hydrolyzation haappens
27
GNEF for EFTu and eEF1A
EFTs and eEF1Ba
28
3' end of tRNA travels into peptidyl transferase centre
accomodation
29
what does peptide bond formation involve
transfer of polypeptide chain form the tRNA in the P site to the AAtRNA in the A site this pulls the aatRNA in the A site into teh P site partway thorugh is a hybrid state
30
what does accomodation lead to
puts the aatRNA and the peptidyl RNA in the active site for catalasys
31
what facilitates the transfer for the peptidyl chain to the aatRNA
2'OH of peptidyl tRNA attracts a proton from the terminal amino group thereby increasing nucleophilicity of the nitrogen which is why amino acid must be attatcehd to 3'OH
32
what amino acid cant polymerize
proline
33
why cant proline polymerize
has only 1 proton availbale to participate in nuc attack- not labile
34
what is proline
imino acid
35
how slow is proline incorporated
15-25x more slowly- might cause stalling or arrest
36
what does EFP do
aleciates ribosomal stalling due to three or more consecutive prolines
37
counterpart to EFP
eIF5A
38
how does EFP and eIF5A work
positions itself between E and P sites of ribosomes and stimulates peptide bond formation
39
what does the activity of EFP and eIF5A depend on
unusual post transcriptional modification (rhamnosulation of hypusinylation)
40
what happnes as the peptide chanin is transfered to the tRNA in the A site
A site tRNA ratchets intot he P site displacing the 3' end of the enpty tRNA into the E site (hybrid state)
41
what happnes in transolation
mRNA bound to tRNA in the A nad P site finishes ratcheting through the ribosome which opens A site for new tRNA and tRNA in E site is positioned to leave
42
what do EFG and eEF2 do
bidn to A site and promote structural rearrangements- latent GTPase ACTIVATED BY L7/12 STALK
43
eEF2 contains what
dipthamide- post trnaslationally modified histidine in all euk and arcahe and unique oto eEF2
44
where is diphatmide found
in eEF2
45
backbone fo 3 methyl groups in dipthimdie
come from s-adenosylmethionine
46
what does diphthimide do
makes cells susceptible to bacterial toxins
47
what does diptheria toxin do
ADP ribosylates dipthimide
48
lack of dipthimide
result sin elevated -1 framshifts
49
mimmics of tRNA
EFG similar to EFTu-tRNA class 1 releease factors mimmic tRNA
50
destablizes aatRNA binding
tetracycline
51
prevents EFTu dissociation
kirromycin
52
promotes mispairing
aminoglycosides
53
inhibits peptidyl transferase
chloramphenicol
54
block peptide exit tunnel
erythromycin and tylosiin
55
caues premature chain termination
puromycin
56
blocks translocation
thiosterepton
57
aminonucleoside antibiotic
puromycin
58
puromycin strutcure
resembles aminoacylated tRNA and enteres the A site and transfers to growing chian forminh puromycylated protein chian leading to premature release

3207 (21 decks)

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