14-18 contd

Question 1

changes ot AA after it has been added to tRNA in vivo

Answer 1

transamidation
selenocysteine and pyrrolysine
cysteine desulfurase
initiator tRNA in prokaryotes

Question 2

aa and aminoacylated tRNA synthetase

Answer 2

aa normally have a corresponding AAtRNA synthetase indicated by a superscript
actual attatched is three letters in front

Question 3

classic chaperville experiment

Answer 3

found that alanine was incorporated at the cystein codons in vitro assay in raney nickel experiment- demonstrated that translation macheinery is unable to distringuish an incorrect from a correct AA

Question 4

enzymes for attatching what to the cognate tRNAs are missing?

Answer 4

attatching glutamine and aspargine

the aaRS are missing not cognate tRNAs!!!!!!

Question 5

how is gluatmine added to its cognate tRNA

Answer 5

GluRS adds glutamic acid to tRNAGln
(aspartic acid) added by AspRS to tRNAAsn

transamination reaction by transamidase makes an acid an amide producing the correct one

Question 6

what must be able to distinguish what

Answer 6

GluRS and AspRS must recognize two tRNAs and transamidase must distinguish between the two charged tRNAs

Question 7

what is methanococcus jennaschii missing

Answer 7

cysRS

Question 8

how is cystine added onto its tRNA if it is missing

Answer 8

phsophorylated serine is added by SepRS
cystein desulfurase converted it to cystein

Question 9

initiator tRNAMet

Answer 9

it and only it is used for initiation and must be recognized by the initiation apparatus for begining

Question 10

initatior tRNA in euk and bacteria

Answer 10

tRNAiMet in euk
tRNAfMet in bacteria (formyl methionine) by transformyase which distinguishes bw that initiatior met tRNA and regular Met tRNA

Question 11

what chaperones charged tRNAs to ribosome

Answer 11

eEFIA and EFTu- anciliary elongation factors

Question 12

eEFIA and EFTu binding to tRNA

Answer 12

they dont

Question 13

what must recognize both tRNAmet and tRNAimet

Answer 13

MetRS in bacteria

Question 14

providing necessary supoort tot he primary activities or operation of an orginization institutaion, or system

Answer 14

anciliary factors

Question 15

where does the start codon go in the ribosome

Answer 15

in the P site

Question 16

what must the assembly process ensure

Answer 16

that no synth occurs until peices are in place
keeping many components inactive druing assmely process

Question 17

how many ancilliary initiation factors in bacterai are needed

Answer 17

3

Question 18

what positinos AUG in bacteria

Answer 18

16S rRNA binds to shine delgarno sequence (anti shine delgarno sequnece)- guides AUG in P site
special initiatio- fMet-tRNAiMet

Question 19

shine delgarno sequnece features

Answer 19

purine rich sequence jsut upstream of the start codon
variations in this sequence of 16s rRNA leads to variation in the level of expression

Question 20

consensus sequence for shine delgarno

Answer 20

AGGAGG
deviations lead regulate strength of translation initiation

Question 21

what is different in large subunit binding to small subunit before synth

Answer 21

must not bind until everything is ready and in place

Question 22

what binds first to small subunit in bacteria

Answer 22

mRNA (shine delgarno) binds to 16s in small subunti via anti shine delgarno

Question 23

what are the threee anciliary factors for initiation of translation in bacteria

Answer 23

IF1, IF2, IF3

Question 24

what do IF1, IF2, and IF3 do

Answer 24

IF1- blocks A site
IF3- blocks E site
IF1 and IF3 prevent large subunit from associaing

IF2- PLAYS A ROLE IN THE ASSOCITION OF INITATIOR TRNA BUT CAN COME SEPARETLY FROM IT and can assocaite in 3 ways (come after, come before, or simultaneous)

DOES NOT BRING IT TO THE P site

Question 25

what removes IF1 and IF3

Answer 25

hydrolysis of GTP on IF2 dissociates all three factors as IF2 is a latent GTPase

Question 26

latent GTPase

Answer 26

if2 donsent hydrolze GTP quickly so we need a GAP to activate its GTPase activitity it serevs as a timing mechanism bc its activity depends on a prior event happening

Question 27

what does IF2 do with the ribosome

Answer 27

accelerates the rate of 30s and 50s subunits joining and this joining triggers GTP hydrolyss by IF2 thorough its GAP allowing maturation steps that enable 70s to enter elongation step

Question 28

actively promotes the transition to the elongation competent conformation

Answer 28

IF2

Question 29

GTP hydrolysis energy

Answer 29

is likey not used to driv the large and small subunits joining

Question 30

true or false: the L12 stalk is the GAP for IF2

Answer 30

false

Question 31

what are all the latent GTPases

Answer 31

eIF2, eIF5B, IF2

Question 32

what do GTPases do

Answer 32

catalyze GTP hydrolysis triggering conformational changes linked with orderly progression of the ribosome through translation

Question 33

antibiotics function

Answer 33

kill or disrupts organism growht that traget bacterial/ fungal processes without disrupting same ones in mamals thorugh samml difference in translation bw bacteria and euk

Question 34

where do antibiotics bind

Answer 34

to critical regions fo the ribosome or to translation factors

Question 35

kasugamycin antibiotic

Answer 35

indirectly induces dissocitaion of P site bound fmet-tRNAfmet from 30s subunit through perturnatio of mRNA