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SFM > Protein processing > Flashcards

Protein processing Flashcards

1
Q

Ribosomes

A

large complexes of proteins and rRNA.
subunits assemble together into active complex in the presence of mRNA
3 sites:
A - Acceptor site (mRNA codon exposed to receive aminoacyl tRNA, except methionine tRNA)
P - Peptidyl site (where aminoacyl tRNA is attached)
E - Empty or Exit site (location occupied by empty tRNA before exciting ribosome)

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2
Q

streptomycin

A

inhibits initiation step (prok)

binds to 30S subunit

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3
Q

Tetracycline

A

inhibit elongation step (prok)

binds to 30s subunit

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4
Q

Shiga toxin

A

inhibit elongation step (euk)

binds to 60S to disrupt elongation

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5
Q

Ricin toxin

A

inhibits elongation step (euk)

binds 60S subunit and blocks entry of aminoacyl tRNA to ribosome complex

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6
Q

puromycin

A

inhibits elongation step (prok/euk)
- resembles 3’ end of aminoacylated tRNA and enters A site so no new AA can enter
used in the LAB

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7
Q

Chloramphenicol

A

inhibits elongation step (prok/mit)

inhibits peptidyl transferase

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8
Q

Cyclohexamide

A

inhibits elongation step (euk)

inhibits peptidyl transferase and impairs peptide bond formation

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9
Q

Clindamycin

A

inhibits elongation step (prok)

bind to 50s Subunit and disrupt translocation

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10
Q

Diptheria Toxin

A

inhibits elongation step (euk)

inactivates EF2-GTP

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11
Q

Protein sorting - cytoplasmic pathway

A

proteins destined for cytosol, mitochondria, nucleus, and peroxisomes
initial synthesis begins AND ends on free ribosomes in cytosol

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12
Q

Protein sorting - secretory pathway

A

proteins destined for ER, lysosomes, plasma membrane, or secretion

  • TSN begins on free ribosomes but terminates on ribosomes sent to ER
  • proteins have ER targeting signal sequence on 1st 20 AA on polypeptide
  • all proteins go through ER lumen for quality control, then to golgi apparatus
    • SRP binds ER target signal and hugs ribosome during translation, then tethers it to ER membrane and temporarily halts translation
  • translation continues and protein is fed through protein translocator into ER lumen, enzymes on luminal side cleave protein
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13
Q

cytoplasm protein signal

A

no signal

cytoplasmic pathway

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14
Q

mitochondrial protein signal

A

a-helix signal made of N-terminal hydrophobic a-helix

cytoplasmic pathway

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15
Q

proteins destined for nucleus

A

Lysine and Arginine rich

cytoplasmic pathway

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16
Q

peroxisome protein signal

A

sequences rich in serine, lysine, and leucine (SKL)

cytoplasmic pathway

17
Q

ER protein signal

A

KDEL (lysine, asparagine, Glutamine, leucine)

- secretory pathway

18
Q

Plasma membrane signal

A

N-terminal apolar residues

- secretory pathway

19
Q

Lysosome protein signal

A

Mannose 6-Phosphate

- secretory pathway

20
Q

Secreted protein signal

A

Trp rich domain

  • secretory pathway
  • put into vesicles and fuse with the PM
21
Q

Mitochondrial protein import

A

proteins meant for specific place in mitochondria

  • unfolded proteins protected by HSP 70 (chaperones so they don’t get degraded)
  • two channels: (TOM on Route membrane and TIM on inner membrane)
  • pores are so small that proteins have to be unfolded to get in
22
Q

nuclear protein import

A
  • nuclear pores are large enough for small folded proteins to enter
  • large proteins need nuclear localization signal (four continuous basic residues)
23
Q

Inclusion Cell disease

A
  • secretory pathway disease
  • lysosomal proteins not tagged with M6P because they have defective or missing GlicNAc phosphotransferase
  • proteins are not phosphorylated, therefore not sorted into vesicles and not transferred to lysosome
  • instead carried to surface and secreted (found in blood)
24
Q

Protein folding

A

large proteins need help folding, can’t risk aggregation or proteolysis
chaperone proteins - HSP70
chaperonin proteins - HSP60 (barrel shaped), fold in ATP dependent manner

25
Q

acetylation

A

post-translational modification
- covalent linkage to amine (NH3+) on Lysine
- uses Acetyl CoA as donor
histone proteins are acetylated (HAT) and de acetylated (HDAC)

26
Q

O-Glycosylation

A

works through serine (has an O in it), O gets removed and sugars are added
- post translational modification

27
Q

N-Glycosylation

A

post-translational modification
- requires asparagine
important for people ith diabetes and elevated blood sugars, cataract tissues many times are glycosylated

SFM (11 decks)

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