Lec 10. Protein synthesis 3. Translation

Question 1

Ribosomal RNAs (rRNAs) are transcribed by what?

Answer 1

RNA pol I and RNA pol III

Question 2

What is the size category for rRNA?

Answer 2

Mid-range to long

Question 3

What is the role of rRNA in the cell?

Answer 3

Components of the ribosome

Question 4

True or False? the ribosome is highly conserved

Answer 4

True

Question 5

What are the two parts to the ribosome?

Answer 5

Large + small subunits

Question 6

What is the ribosome composed of?

Answer 6

RNA+potein

Question 7

Is the ribosome a ribozyme?

Answer 7

Yes

Question 8

What are the three binding sites for tRNA?

Answer 8

A.P.E

Question 9

What does the A stand for?

Answer 9

Attachment

Question 10

What does the P stand for?

Answer 10

Peptide bond (where peptide bond is forming)

Question 11

What does the E stand for?

Answer 11

Exit

Question 12

Transfer RNAs tRNAs are transcribed by what?

Answer 12

RNA Pol III

Question 13

What is the size category for tRNAs?

Answer 13

Mid-range

Question 14

What is the role of tRNA in the cell?

Answer 14

Deliver amino acids to the growing polypeptide chain

Question 15

What are some tRNA characteristics?

Answer 15

Unique splicing mechanism. Modified nucleotides are abundant. Fewer tRNAs are needed than are codons in the table. Each tRNA has a special tRNA synthetase that adds the appropriate amino acid

Question 16

Pertaining to tRNA, how modified nucleotides are abundant, what do some of these modification do?

Answer 16

Help distinguish tRNA(i)-Met from normal elongating tRNA-met. Since tRNA(i)-Met folds differently

Question 17

Why are fewer tRNA needed than codons in the table?

Answer 17

Wobble position

Question 18

What is the wobble position?

Answer 18

Last position of the codon doesnt have to match perfectly.

Question 19

What is a substantial source of translational error?

Answer 19

Incorporating the incorrect amino acid to a tRNA while undergoing the 2nd proofreading step (clipping off the amino acid if its wrong)

Question 20

Before starting translation initiation what two things are needed?

Answer 20

A 5’ cap and a 3’ poly-A tail

Question 21

What are the steps to translation initiation?

Answer 21

1. Small subunit binds mRNA first. 2. tRNA(i)-Met binds to the P site. 3.Small subunit+tRNA(i)-Met scans the 5’UTR until it finds AUG. 4. elFs dissociate when large subunit binds. 5.Circularized mRNA facilitates ribosome recycling.

Question 22

What are 6 important translation initiation factors?

Answer 22

elF1, elF2, elF3, elF4F, elF5, elF6

Question 23

Which of the translation initiation factors is a complex?

Answer 23

elF4F

Question 24

What does elF1 do?

Answer 24

blocks tRNA(i)-Met from entering A/E sites

Question 25

What does elF2 do?

Answer 25

loads tRNA(i)-Met at P site

Question 26

What does elF3 do?

Answer 26

loads small subunit onto mRNA, recruits other elFs, promotes scanning, prevents large subunit binding

Question 27

What does elF4F do?

Answer 27

binds the mRNA 5'cap

Question 28

What does elF5 do?

Answer 28

releases other elFs to allow large subunit binding once AUG found

Question 29

What does elF6 do?

Answer 29

Prevents large subunit binding

Question 30

What are the steps to translation elongation?

Answer 30

1. An aa-tRNA enters the A site. 2. The peptide bond forms. 3.The large subunit slides. 4. The small subunit slides down the mRNA, the tRNA is ejected 5. Repeat

Question 31

Pertaining to prokaryotes, what elongation factor recruites aa-tRNA to A site (a G protein)?

Answer 31

EF-Tu

Question 32

Pertaining to Eukaryotes, what elongation factor recruites aa-tRNA to A site (a G protein)?

Answer 32

eEF1B

Question 33

Pertaining to prokaryotes, what elongation factor regenerates ^(up) (a GEF)?

Answer 33

EF-Ts

Question 34

Pertaining to Eukaryotes, what elongation factor regenerates ^(up) (a GEF)?

Answer 34

eEF1A

Question 35

Pertaining to prokaryotes, what elongation factor helps ribosome translocation (a g protein)?

Answer 35

EF-G

Question 36

Pertaining to Eukaryotes, what elongation factor helps ribosome translocation (a g protein)?

Answer 36

eEF2

Question 37

what do G proteins do?

Answer 37

hydrolyze GTP

Question 38

What do GEFS do?

Answer 38

Regenerate G proteins by swapping the spent GDP from fresh GTP

Question 39

What do GAPS do?

Answer 39

Stimulate G proteins to hydrolyze GTP

Question 40

True or False? Translation elongation is highly error prone at fast speeds

Answer 40

False. Slow speeds

Question 41

During translation elongation what speeds up the process and increased fidelity?

Answer 41

Elongation factors

Question 42

Pertaining to translation termination, eRFs (release factors) are proteins that are shaped like tRNAs but they do not

Answer 42

Carry an amino acid for the growing polypeptide chain

Question 43

eRF1 works together with that other release factor?

Answer 43

eRF3

Question 44

What does eRF3 do?

Answer 44

GTPase (hydorlyze GTP)

Question 45

What does eRF1 do?

Answer 45

interacts with stop codon

Question 46

What does NDM stand for?

Answer 46

Nonsense mediated decay

Question 47

What do nonsense mutations cause?

Answer 47

Premature stop codons

Question 48

What are the two other observations for NMD?

Answer 48

10% of all genetic diseases result from nonsense mutations. RNAs containing NMDs are underrepresented in cellular transcriptome

Question 49

What is NMD?

Answer 49

is the detection and degradation of mRNAs harboring premature stop codons

Question 50

What important proteins interact with NMD?

Answer 50

UPF (up-frameshift) SMG (suppressor of morphogenesis in genetalia) and eRFs

Question 51

What two pathways trigger NMD?

Answer 51

Incorrect splicing retains exon junction proteins and 3' UTR is too long (stop codon came too soon)

Question 52

What is selenocysteine?

Answer 52

21st amino acid

Question 53

What does selenocysteine do?

Answer 53

Recognizes what is supposed to be a STOP codon AUG

Question 54

What happens when we cant find tRNA selenocysteine?

Answer 54

NMD

Question 55

What do chaperone proteins do?

Answer 55

Help newly transcribed proteins fold correctly.

Question 56

What are three options when proteins are misfolded?

Answer 56

try again: refold in chaperone, Destroy: recycle in proteasome, Escape detection: aggregate and cause disease.

Question 57

How are misfolded proteins degraded?

Answer 57

Tagged for degradation in proteasome (polyubiquitinated).