4-2: Translation

Question 1

What are proteins

Answer 1

Polypeptides
Polymers of aa connected by peptide bonds

Question 2

Structure of aa…

Answer 2

Amino group, alpha carbon with R group, carboxyl group

Question 3

What are joined by peptide bonds

Answer 3

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

Question 4

How are the aa grouped

Answer 4

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

Question 5

What are the two rare aa

Answer 5

Selenocysteine, pyrrolysine

Question 6

What is protein primary structure

Answer 6

Aa sequence in a protein

Question 7

What is protein secondary structure

Answer 7

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

Question 8

What is protein tertiary structure

Answer 8

Full 3D structure, multiple secondary structure elemented arranged

Question 9

What is protein quaternary structure

Answer 9

Multiple peptides come together (multimeric proteins)

Question 10

What are protein domains

Answer 10

Structural or functional segments of a protein

Question 11

What is the helix-turn-helix (HTH)

Answer 11

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

Question 12

What structures are involved in tRNA

Answer 12

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

Question 13

Enzymes that charge tRNAs are… What do they do

Answer 13

tRNA synthetases
Add amino acid to CCA at 3’ end

Question 14

Does one codon encode one amino acid?

Answer 14

No, multiple codons can encode one aa

Question 15

What are the translation start codons

Answer 15

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

Can also be GUG, UUG

Question 16

What is the start codon translated to

Answer 16

N-formylmethionine (fMet)

Question 17

Does AUG always encode fMet

Answer 17

No, unless it is start codon it encodes normal Met

Question 18

What are the three stop codons

Answer 18

UAA, UGA, UAG

Question 19

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

Answer 19

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

Question 20

What are ribosomal subunits made of?

Answer 20

rRNA and ribosomal proteins

Question 21

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

Answer 21

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

Question 22

Are the small and large subunits always together

Answer 22

No, associate and dissociate during translation

Question 23

What carries out the main function of ribosome

Answer 23

rRNA

Question 24

How is translation initiated

Answer 24

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

Question 25

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

Answer 25

Shine-Dalgarno sequence

Question 26

What are the 3 tRNA binding sites of the ribosome

Answer 26

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

Question 27

What is the A site

Answer 27

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

Question 28

What is the P site

Answer 28

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

Question 29

What is the E site

Answer 29

uncharged tRNA exits

Question 30

What is elongation

Answer 30

The growth of the peptide chain

Question 31

When does translation end

Answer 31

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

Question 32

Multiple ribosomes on a single mRNA simultaneously is...

Answer 32

Polysomes

Question 33

What is transcription/translation coupling

Answer 33

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

Question 34

How is eukaryotic translation different

Answer 34

No coupling (transcri in nucleus, transl in cytoplasm) mRNA only encodes one gene Initiation step different (5' cap recognized) Ribosome larger: 40S + 60S = 80S

Question 35

Protein folding either occurs...

Answer 35

Spontaneously or uses chaperones

Question 36

what are chaperones

Answer 36

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

Question 37

Functions of chaperones

Answer 37

Initial folding, re-folding denatured

Question 38

Energy source of chaperons?

Answer 38

ATP hydrolysis

Question 39

When are chaperons activates

Answer 39

High or low temperatures to assist with folding

Question 40

How do proteins get out of the cytoplasm into different locations

Answer 40

Translocase systems

Question 41

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

Answer 41

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

Question 42

What are the two secretion systems

Answer 42

Sec secretion system Twin arginine translocase (tat)

Question 43

What does the tat pathway do

Answer 43

Secretes pre-folded proteins across membrane

Question 44

What does the sec secretion do

Answer 44

Recognizes signal in first 20 aa, translocates unfolded protein

Question 45

What are the two sec pathways

Answer 45

passed across cytoplasmic membrane (SecA) Recognized by RNA/protein complex and inserted into membrane (SRP)

Question 46

What does the SecA pathway do

Answer 46

Pass unfolded proteins across cytoplasmic membrane

Question 47

What does the SRP sec pathway do

Answer 47

Protein recognized by signal recognition particle and inserted into membrane

Question 48

Both SRP and SecA...

Answer 48

Pass unfolded protein through membrane channel