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MCM Exam II > Functions and Dysfunctions of Protein Processing > Flashcards

Functions and Dysfunctions of Protein Processing Flashcards

1
Q

nonsense mutation

A

codon changes into a stop codon

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2
Q

cause of sickle cell anemia

A

missense mutation of 6th codon in the allele of the gene for human beta-globin (HBB)

GAG –> GTG
Glutamate (hydrophilic) –> Val (hydrophobic)

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3
Q

cause of Duchenne muscular dystrophy

A

large in frame and out of frame deletions to the dystrophin gene

results in little to no expression of the dystrophin protein

in frame deletions result in milder form (Becker muscular dystrophy)

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4
Q

3’ CCA terminal region

A

region of tRNA that binds the AA that matches the corresponding codon

makes sure that the correct AA is being matched

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5
Q

two step process of amino acid activation

A
  1. aminoacyl tRNA synthetase catalyzes addition of AMP to COOH end of AA (AA + AMP)
  2. AA transferred to cognate tRNA (AA + tRNA)
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6
Q

aminoacyl tRNA synthetase

A

serves as the second genetic code

is specific for each AA

maintains the fidelity of protein synthesis but ensuring the correct AA is bound

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7
Q

EIF2, 4E, 4G

- what are these

A

Eukaryotic initiation factors

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8
Q

Shine delgarno sequence

A

Site of initiation for prokaryotes

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9
Q

Initiator tRNA

A

Binds to GTP during initiation, which is bound to the P site of the small subunit; forms the methioninyl tRNA

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10
Q

What do elongation factors do

A

Proofreading

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11
Q

Release factors

A

Recognize stop codons and promote the release of completed proteins from the tRNA; they bind to the A site and cleave the ester bond between the C terminus of the polypeptide and the tRNA

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12
Q

What dissociates the ribosomal complex

A

GTP hydrolysis

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13
Q

How does streptomycin work

A

Binds to 30S subunit of prokaryotic ribosomes to disrupt initiation of translation; interferes with the binding fmet-tRNA; interferes with 30s subunit association with the 50s subunit

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14
Q

How does shiga toxin work

A

Binds to the 60s subunit of eukaryotic ribosomes to disrupt elongation

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15
Q

How do clindamycin and erythromycin work

A

They bind to the 50s subunit of prokaryotic ribosomes to disrupt translocation of the ribosome; commonly used to treat pertussis

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16
Q

How do tetracyclines work

A

They bind to the 30s subunit of prokaryotic ribosomes to disrupt elongation; blocks the entry of aminoactyl tRNA to the ribosomal complex

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17
Q

What does initiation require to start

A

Hydrolysis of one GTP (equivalent to one ATP)

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18
Q

What does elongation require

A

Hydrolysis of two GTP per amino acid added (equivalent to two ATP)

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19
Q

What does termination require

A

Hydrolysis of one GTP (equivalent of one ATP)

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20
Q

How does the diptheria toxin work

A

Inactivates GTP bound to eEF-2 and inhibits elongation in eukaryotes

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21
Q

How does chloramphenicol work

A

Inhibits peptidyl transferase in prokaryotes and mitochondria, which forms the peptide bond between the amino acid in the A site with the AA in the P site

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22
Q

How does cycloheximide work

A

Toxin from streptomyces griseus

Inhibits peptidyl transferase in eukaryotes; blocks elongation

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23
Q

Puromycin

A

From streptomyces alboniger

Causes premature chain termination in prokaryotes and eukaryotes; resembles the 3’ end of aminoacylated tRNA and enters the A site which stops the ribosome

Inhibits elongation

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24
Q

Proteins that use the cytoplasmic pathway for protein sorting are destined for where

A

Cytosol, mitochondria, nucleus, peroxisomes

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25
Q

Proteins that use the secretory pathway for protein sorting are destined for where

A

ER, lysosomes, plasma membranes, or for secretion

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26
Q

What type of amino acid chains are characteristic of the cytoplasmic pathway

A

Hydrophobic

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27
Q

What kind of amino acids are characteristic of the secretory pathway

A

Positive charged

NH3+

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28
Q

The proteins going to the nucleus in the cytoplasmic pathway are special in what way

A

Rich in lysine and arginine

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29
Q

The proteins going to the peroxisome are special in what way

A

They have an SKL sequence

30
Q

Proteins destined for the mitochondria in the cytoplasmic pathway of protein sorting are special in what way

A

N terminal hydrophobic alpha helix

Require TIM and TOM

31
Q

N terminal hydrophobic alpha helix

A

Sequence for proteins destined for the mitochondria in protein sorting

Helps the proteins interact with chapter one proteins

32
Q

TIM and TOM

A

Transporter in inner membrane (TIM)

Transporter in outer membrane (TOM)

Transporters that pass protein across the mitochondrial membranes

33
Q

Heat shock proteins 70 (HSP70)

A

Important chaperone that protects unfolded proteins in the mitochondria

34
Q

How are proteins destined for the nucleus imported

A

through nuclear pores; small proteins don’t have to unwind; large proteins require nuclear localization signals

35
Q

Translocation signal for proteins destined fro the mitochondria

A

N terminal hydrophobic alpha-helix signal peptide

36
Q

Translocation signal for proteins destined for the nucleus

A

KKKRK signal sequence

37
Q

Translocation signal for proteins destined for the peroxisomes

A

C-terminal SKL signal sequence

38
Q

Translocation signal for proteins destined for the ER lumen

A

C-terminal KDEL retention signal

K - lysine
D - aspartic acid
E - glutamic acid
L - leucine

39
Q

Translocation signal for proteins destined for lysosomes

A

Mannose-6-phosphate signal group

Disease: I-cell disease

40
Q

Translocation signal for proteins destined for secretion

A

Tryptophan-rich domain signal region absence of retention motifs

41
Q

Translocation signal for proteins destined for the membrane

A

N-terminal apolar region (stop transfer sequence)

42
Q

Each protein in the secretory pathway has what

A

An ER—targeting signal peptide (15-60 amino acids at N terminus of the protein)

  • 1-2 basic amino acids (Lys or Arg) near N terminus
  • extremely hydrophobic sequence on C terminus
43
Q

Signal recognition particle (SRP)

A

In the secretory pathway

Binds to the ER-targeting signal on the protein and the ribosome during translation; wraps itself around the ribosome-mRNA-peptide complex, tethering it to the ER membrane and halting translation temporarily

44
Q

I-cell disease

A

Severe form of lysosomal storage disease; Defect in tagging of lysosomal proteins with mannose 6-P; lysosomes won’t be able to break down molecules which causes a large # of symptoms

45
Q

Chaperones

A

Protects large proteins and helps them fold into proper tertiary structure

Ex: HSP70 (uses ATP)

46
Q

Chaperonins

A

Have barrel shaped compartments that admit unfolded proteins and catalyze their folding in an ATP dependent manner

Ex: HSP60 (uses ATP)

47
Q

How does proteolytic cleavage work

A

Unmasking the active site which converts inactive forms to active enzymes
Trypsinogen —> chymotrypsinogen
Trypsin —> Chymotrypsin

Also converts nascent precursor proteins to mature ones
Proinsulin —> insulin

48
Q

Acetylation

  • what type of linkage
  • functional group
  • where does it get the functional group
  • happens to what amino acid post translationally
A

Covalent linkage to amine
Amine (-NH3+)
Acetyl CoA
Lysine

49
Q

O-Glycosylation

  • what proteins
  • Functional group
  • happens to which amino acids post translationally
A

extracellular proteins (cell surface and plasma proteins)
Hydrolysis (-OH)
Serine, threonine

50
Q

N-glycosylation

  • what proteins
  • functional group
  • happens to which amino acids post translationally
A

extracellular proteins
Acid-amine (-CONH2)
Asparagine

51
Q

Phosphorylation

  • linkage
  • functional group
  • happens to which amino acids post translationally
  • what is the purpose
A

Ester bond between phosphate and -OH of AA
Hydroxyl (-OH)
Serine, tyrosine, threonine
- also aspartate, histidine
regulates enzyme activity, protein function, cell growth

52
Q

Disulfide bonds

  • linkage
  • functional group
  • happens to which amino acids post translationally
  • where does this occur
  • facilitated by
A 
Oxidation —> covalent linkage of cysteine residues
Sulfhydryl (-SH)
Cysteine
ER lumen
protein disulfide isomerases
53
Q

Disulfide bonds in post translational modification

A

Form between thiol (SH) group of 2 cysteine residues

Occurs in the ER lumen

54
Q

Protein disulfide isomerases

A

Facilitates disulfide bond formation in post translational modification of proteins

55
Q

Ehlers-Danlos Syndrome

A

Results from a defect in Lysyl hydroxylase in post translational modification; cannot assemble collagen correctly

Characterized by overly flexible joints, blood vessel walls, intestines, or ruptured uterus

56
Q

Epidermolysis Bullosa Symplex

A

Defect in lysyl hydroylase; cannot form collagen correctly

Blisters on skin

57
Q

How does Alzheimer’s disease form

A

Misfolding/aggregation of amyloid beta peptide (AB) that forms plaques in the brain WITH hyperphosphorylation of Tau (microtubullary stimulating agent)

58
Q

Sporadic form cause versus familial form cause of AD

A

Familial: mutations in APP (Amyloid precursor protein) and Tau

Sporadic: brain aging

59
Q

How is Parkinson’s caused

A

Aggregation of a-synuclein (AS) forms insoluble fibrils that deposit as Lewy bodies in dopaminergic neurons in substantial nigra

Selective death of these neurons and reduced availability of dopamine

60
Q

Familial form of PD versus sporadic form

A

Familial: mutations in AS (a synuclein)

Sporadic: brain aging

61
Q

How is Huntington’s disease caused

A

Mutation in the Huntington gene that causes expansion of CAG triplet repeats

Results in polyglutamine repeats, forming intramolecular H-bonds which will misfold and aggregate

Selective death of cells in basal ganglia

62
Q

How is Creutzfeldt-Jacob disease caused

A

Misfolding of prion proteins

It’s a type of transmissible spongiform encephalopathies

63
Q

missense mutation

A

changes amino acid

64
Q

frameshift mutation

A

one or more nucleotides are deleted or inserted into out of frame; change in the codon sequence and consequently alteration in the amino acid sequence

65
Q

aminoacyl tRNAs

A

tRNA + amino acid

catalyzed by aminoacyl tRNA synthetase

66
Q

what forms during initiation of translation (3 things)

A

formation of 1) mRNA, 2) small ribosomal subunit, and 3) initiator tRNA pre-initiation complex

67
Q

what are the three stop codons

A

UAA
UAG
UGA

68
Q

what does the release factor do

A

cleaves ester bond between C terminus of polypeptide and the tRNA

catalyze the addition of water instead of an AA

69
Q

HSP60

A

heat shock protein 60

chaperonin; folds large proteins

70
Q

what is essential for activity of lysyl and prolyl hydroxylase

A

ascorbic acid

MCM Exam II (14 decks)

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