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MICRB 265 > 4-2: Translation > Flashcards

4-2: Translation Flashcards

1
Q

What are the two rare AA?

A

Selenocysteine, pyrrolysine

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2
Q

What are protein domains

A

Structural or functional segments of a protein

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3
Q

What is the helix-turn-helix (HTH)

A

Protein domain that binds DNA, found in DNA binding regulatory proteins. Found in hundreds of proteins of the Salmonella genome.

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4
Q

What structures are involved in tRNA

A

70-95 bases long, extensive structures that often contain modified bases (eg. mG)

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5
Q

What are tRNA synthetases? What do they do?

A

Add cognate amino acid to CCA at 3’ end of tRNA to “charge” them

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6
Q

What are the translation start codons

A

Encode for first aa of ORF
Usually AUG (83%)
Can also be GUG, UUG

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7
Q

What is the amino acid that the start codon is translated to in bacteria?

A

N-formylmethionine (fMet)

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8
Q

Does AUG always encode fMet?

A

No, unless it is start codon it encodes normal Met

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9
Q

What are the three stop codons

A

UAA, UGA, UAG

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10
Q

The prokaryotic ribosome is made up of what subunits?

A
  • 30S (small) subunit
  • 50S (large) subunit
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11
Q

What is the size of the prokaryotic ribosome in Svedberg units?

A

70S ribosome

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12
Q

What are ribosomal subunits made of?

A

rRNA and ribosomal proteins

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13
Q

What are the E coli 30S and 50S ribosome subunits made of

A

30S = 16S rRNA, 21 proteins
50S = 5S/23S rRNA, 31 proteins

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14
Q

What carries out the main function of ribosome

A

rRNA - responsible for catalyzing peptide bond formation

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15
Q

How is translation initiated

A

16S rRNA in 30S subunit binds to the ribosomal binding site that is correctly spaced from the start codon AUG

30S binds RBS, fMet tRNA binds AUG

50S subunit recruited using GTP to form the full 70S ribosome

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16
Q

The ribosomal binding site (RBS) is also known as what?

A

Shine-Dalgarno sequence

17
Q

What are the 3 tRNA binding sites of the ribosome

A
  1. A (aminoacyl) site
  2. P (peptidyl) site
  3. E (exit) site
18
Q

What is the A site

A

New charged tRNA’s enter, recognize codon needing aa

Growing peptide from P site transfers to aa in A site

19
Q

What is the E site

A

uncharged tRNA exits

20
Q

When does translation end

A

Stop codon encountered, release factor protein binds, releasing peptide and mRNA. Ribosome dissociates

21
Q

What is used as the energy source in translation?

A

GTP

22
Q

What are polysomes?

A

Multiple ribosomes on a single mRNA simultaneously translating

23
Q

When can polysomes form?

A

When the 5’ end of RNA in an ORF is translated and freed up

24
Q

What is transcription/translation coupling

A

RNA is being translated as it is still being transcribed

25
Q

How is eukaryotic translation different from bacterial?

A

No coupling of translation and transcription

Initiation step different (5’ cap recognized)

Ribosome larger: 40S + 60S = 80S

26
Q

what are chaperones

A

Proteins that help other proteins adopt their properly folded/active states

27
Q

Functions of chaperones

A

Initial folding, re-folding denatured proteins, helping subunits in multimeric proteins come together, RNA folding

28
Q

Energy source of chaperons?

A

ATP hydrolysis

29
Q

What can activate chaperones?

A

High or low temperatures (eg. heat chock proteins, cold shock proteins)

30
Q

How do proteins get out of the cytoplasm into different locations

A

Translocase systems

31
Q

Where is the signal sequence found?

A

N terminus

32
Q

What are the two secretion systems

A

Sec secretion system
Twin arginine translocase (tat)

33
Q

What does the tat pathway do

A

Secretes pre-folded proteins across membrane

34
Q

What does the sec secretion do

A

Recognizes signal in first 20 aa, translocates unfolded protein

35
Q

What are the two sec pathways

A

SecA and SRP

36
Q

What does the SecA pathway do

A

Pass unfolded proteins across cytoplasmic membrane

37
Q

What does the SRP sec pathway do

A

Protein recognized by signal recognition particle and inserted into membrane

38
Q

What do both SecA and SRP do?

A

Pass unfolded protein through Sec YEG translocon
Require ATP
Cleave the signal sequence following translocation

MICRB 265 (34 decks)

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