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BIOCHEMISTRY > EXAM2_L17_TRANSLATION > Flashcards

EXAM2_L17_TRANSLATION Flashcards

1
Q

What 4 tools needed for translation?

A
  1. mRNA- coded instructions
  2. tRNA- decodes triple codons
  3. Aminoacyl-tRNA synthetases- attach AA’s to tRNAs w/ anti-codons
  4. Ribosomes- welder
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2
Q

What are the START and STOP codons?

What terminus does synthesis begin?

A

START- AUG (methionine)
STOP- [UGA,UAA,UAG]
-begins at Amino terminus (NH2)-
-first codon is ALWAYS methionine

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3
Q

What does degenerate mean talking about codons?

A

Redundant

- several codons can be used to code for the same AA.

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4
Q

What are the 4 mutations?

A
  1. Missense- base change= AA change
  2. Nonsense- base change= STOP
  3. Silent- base change= SAME AA
  4. Frameshift- insertion/deletion- can induce missense/nonsense/ REALLY BAD
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5
Q

Synthetases vs synthase

A

Synthetases- Require ATP for energy

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6
Q

Aminoacyl-tRNA synthetases

2 steps:

A

Adds AA’s to correct tRNAs

  1. link AA to tRNA w/ ATP
  2. tRNA bind to codon on RNA
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7
Q

Polysome or Polyribosome

A

mRNA can have multiple ribosomes translating it at any given time

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8
Q

2 Ribosomal subunits:
3 binding sites:
Where is peptide bond formed?

A

LARGE- forms peptide bonds
SMALL- binds mRNA & tRNA; initiation; decoding center

“APE”
A- aminoacyl-tRNA site (PEPTIDE BOND FORMS HERE)
P-peptidyl-tRNA site
E-exit site

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9
Q

3 types of Translation factors

how do you determine eukaryote/prokaryote TF?

A
  1. initiation factors (IFs)
  2. Elongation factors (EFs)
  3. Release factors (RFs)

eIF= eukaryotes (“e”- prefix)
IF=prokaryotes

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10
Q

INITIATION/PROKARYOTES:
What sequence used?
Where located?
Where does it bind?

A

Shine-Delgarno (SD) Sequence
-6-10 bp upstream of START
rRNA of small ribosome unit binds START codon in the P Site

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11
Q

INITIATION/EUKARYOTES-
How does mRNA find/attach ribosome?
What proteins used?
What is NOT found

A

5’ cap binds two eIF-4’s (cap binding proteins)
— (positions small ribosomal unit @ mRNA)

NO SD SEQUENCE

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12
Q

7 steps of eukaryotic initiation

A
  1. Charged initiator tRNA binds eIF2/GTP
  2. tRNA/eIF2/GTP binds to SMALL ribosomal subunit
  3. EIF4s bind 5’ end of mRNA
  4. small subunit binds to 5’ end of mRNA
  5. Small RS scans/finds AUG
  6. GTP hydrolyzed
  7. EIF2/GDP dissociates & Large RS joins
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13
Q

Remember eIF2 must release____ and bind new _____ before it can recruit another _______ to the _______.

Where is Met-tRNA deposited in both eukaryotic and prokaryotic translation?

A

eIF2 must release GDP,bind new GTP,before recruit another initiator tRNA to the small subunit

Met-tRNA binds P SITE and next AA’s bind A site

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14
Q

What is conserved between prokaryotes and eukaryotes?

A

elongation process

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15
Q

Eukaryotic Translation Elongation

3 Steps:

A
  1. Charged tRNA escorted by eEF1a/GTP to “A”SITE
  2. GTP hydrolyzed>eEF1a releases tRNA. eEF1a/GDP leaves.
  3. peptidyl transferase forms peptide bond between meth at Psite with incoming aminoacyl-tRNA at Asite.
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16
Q

4-step cycle of adding additional polypeptides

A
  1. translocation “TL” of large subunit
  2. TL of small subunit
  3. binding charged tRNA at A site
  4. Forming peptide bond
17
Q 
Eukaryotic Translation Termination:
How is it initiated?
is tRNA used?
Where  is stop codon bound?
What bond is broken and where?

UGA, UAA, UAG= STOP CODONS

A

-Cell use eRF’s (release factors) that terminate synthesis

NO tRNA w/ STOP codons!!!

–> RF binds STOP codon at A site & hydrolyzes
tRNA:::polypeptide bond at the P Site.

-tRNA released, subunits and mRNA dissociate

18
Q

How do antibiotics affect bacteria and not humans?

A

Prokaryotic and eukaryotic ribosomes and translation mechanisms are different and can be targets for inhibiting bacterial protein synthesis (killing bacteria not humans).

19
Q

What drug inhibits initiation of protein synthesis?

What 4 drugs inhibit elongation?

A

-Streptomycin (inhibits initiation)

Inhibits Elongation:

  1. Tetracycline
  2. Chloramphenicol
  3. Erythromycin
  4. Puromycin
20
Q

What are 3 types of post translational modifications?

Where and when can PTM’s happen?

A
  1. folding
  2. covalent modification
  3. binding
    Nucleus, RER lumen, Cytosol
    Anytime during proteins life
    Alters side chains of AA’s after incorporated into protein
21
Q

Laundry list of Modifications:

A
  1. protein folding
  2. proteolysis (zymogen)
  3. Covalent addition of functional groups/proteins:
    - phosphorylation,
    glycosylation
    , methylation
    , acetylation,
    hydroxylation,
    y-carboxylation,
    ubiquitination
    , add lipids
22
Q

Glycosylation (2 types)

A

add sugar to protein> Glycoprotein

  1. N-linked glycosylation
  2. O-linked glycosylation
23
Q

Methylation- What mediated by?

A

-add CH3
methyltransferases
demethylases

24
Q

Acetylation
What added?
What 2 mediators?
reversible?

A

Adding acetyl COCH3 group
-Histone acetyltransferase (HAT)
-Histone deacetylases (HDAC)
REVERSIBLE!

25
Q

Hydroxylation

A 
adding OH (ie hydroxylation of collagen)
vitC> scurvy
26
Q

y-Carboxylation

What used? what made? What is an example that uses this?

A

PTM of glutamate to generate y-carboxyglutamate
-Uses y-glutamyl carboxylase and vitK as cofactor

ex: proteins involved in blood clotting cascade

27
Q

Ubiquitination

What added? What mediated by? What used for?

A

Adding ubiquitin (Ub)

  • 76-amino acid polypeptide to lysine residues of target protein
  • mediated by ubiquitin ligase
  • Ubiquitin is a tag for protein degredation

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