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MICRB 265 > 4-2: Translation > Flashcards

4-2: Translation Flashcards

1
Q

What are proteins

A

Polypeptides
Polymers of aa connected by peptide bonds

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2
Q

Structure of aa…

A

Amino group, alpha carbon with R group, carboxyl group

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3
Q

What are joined by peptide bonds

A

Carboxylic acid group of one aa, amino group of the next

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4
Q

How are the aa grouped

A

Based off R group properties (non-polar, polar, positively or negatively charged)

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5
Q

What are the two rare aa

A

Selenocysteine, pyrrolysine

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6
Q

What is protein primary structure

A

Aa sequence in a protein

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7
Q

What is protein secondary structure

A

Simple local structure, a-helices or B sheets
H bonds of peptide backbone

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8
Q

What is protein tertiary structure

A

Full 3D structure, multiple secondary structure elemented arranged

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9
Q

What is protein quaternary structure

A

Multiple peptides come together (multimeric proteins)

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10
Q

What are protein domains

A

Structural or functional segments of a protein

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11
Q

What is the helix-turn-helix (HTH)

A

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

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12
Q

What structures are involved in tRNA

A

Anticodon (binds specific three base codon)
At other end, specific amino acid corresponding to the codon

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13
Q

Enzymes that charge tRNAs are… What do they do

A

tRNA synthetases
Add amino acid to CCA at 3’ end

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14
Q

Does one codon encode one amino acid?

A

No, multiple codons can encode one aa

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15
Q

What are the translation start codons

A

Encode for first aa of ORF
Usually AUG (83%) (ATG in DNA)

Can also be GUG, UUG

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16
Q

What is the start codon translated to

A

N-formylmethionine (fMet)

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17
Q

Does AUG always encode fMet

A

No, unless it is start codon it encodes normal Met

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18
Q

What are the three stop codons

A

UAA, UGA, UAG

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19
Q

The prokaryotic ribosome is the… Made up of what subunits?

A

70S ribosome
- 30S (small) subunit
- 50S (large) subunit

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20
Q

What are ribosomal subunits made of?

A

rRNA and ribosomal proteins

21
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

22
Q

Are the small and large subunits always together

A

No, associate and dissociate during translation

23
Q

What carries out the main function of ribosome

A

rRNA

24
Q

How is translation initiated

A

Consensus sequence of ribosomal binding site binds 16S rRNA in 30S subunit, helps ribosome locate AUG codon

30S binds RBS, fMet tRNA binds AUG

50S subunit recruited using GTP

25
Q

The ribosomal binding site (RBS) is also known as…

A

Shine-Dalgarno sequence

26
Q

What are the 3 tRNA binding sites of the ribosome

A
  1. A (aminoacyl) site
  2. P (peptidyl) site
  3. E (exit) site
27
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

Translocation of RNA to P site

28
Q

What is the P site

A

tRNA transfers growing aa chain onto new charged tRNA in the A site, becomes uncharged

29
Q

What is the E site

A

uncharged tRNA exits

30
Q

What is elongation

A

The growth of the peptide chain

31
Q

When does translation end

A

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

32
Q

Multiple ribosomes on a single mRNA simultaneously is…

A

Polysomes

33
Q

What is transcription/translation coupling

A

RNA is being translated as it is still being transcribed (RNAp and ribosome both attached)

34
Q

How is eukaryotic translation different

A

No coupling (transcri in nucleus, transl in cytoplasm)

mRNA only encodes one gene

Initiation step different (5’ cap recognized)

Ribosome larger: 40S + 60S = 80S

35
Q

Protein folding either occurs…

A

Spontaneously or uses chaperones

36
Q

what are chaperones

A

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

37
Q

Functions of chaperones

A

Initial folding, re-folding denatured

38
Q

Energy source of chaperons?

A

ATP hydrolysis

39
Q

When are chaperons activates

A

High or low temperatures to assist with folding

40
Q

How do proteins get out of the cytoplasm into different locations

A

Translocase systems

41
Q

What signals that a protein needs to go to a particular secretion system

A

signal sequence at the N-terminus (first 25 aa)

42
Q

What are the two secretion systems

A

Sec secretion system
Twin arginine translocase (tat)

43
Q

What does the tat pathway do

A

Secretes pre-folded proteins across membrane

44
Q

What does the sec secretion do

A

Recognizes signal in first 20 aa, translocates unfolded protein

45
Q

What are the two sec pathways

A

passed across cytoplasmic membrane (SecA)

Recognized by RNA/protein complex and inserted into membrane (SRP)

46
Q

What does the SecA pathway do

A

Pass unfolded proteins across cytoplasmic membrane

47
Q

What does the SRP sec pathway do

A

Protein recognized by signal recognition particle and inserted into membrane

48
Q

Both SRP and SecA…

A

Pass unfolded protein through membrane channel

MICRB 265 (34 decks)

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