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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
Proteins that use the secretory pathway for protein sorting are destined for where
ER, lysosomes, plasma membranes, or for secretion
26
What type of amino acid chains are characteristic of the cytoplasmic pathway
Hydrophobic
27
What kind of amino acids are characteristic of the secretory pathway
Positive charged NH3+
28
The proteins going to the nucleus in the cytoplasmic pathway are special in what way
Rich in lysine and arginine
29
The proteins going to the peroxisome are special in what way
They have an SKL sequence
30
Proteins destined for the mitochondria in the cytoplasmic pathway of protein sorting are special in what way
N terminal hydrophobic alpha helix Require TIM and TOM
31
N terminal hydrophobic alpha helix
Sequence for proteins destined for the mitochondria in protein sorting Helps the proteins interact with chapter one proteins
32
TIM and TOM
Transporter in inner membrane (TIM) Transporter in outer membrane (TOM) Transporters that pass protein across the mitochondrial membranes
33
Heat shock proteins 70 (HSP70)
Important chaperone that protects unfolded proteins in the mitochondria
34
How are proteins destined for the nucleus imported
through nuclear pores; small proteins don’t have to unwind; large proteins require nuclear localization signals
35
Translocation signal for proteins destined fro the mitochondria
N terminal hydrophobic alpha-helix signal peptide
36
Translocation signal for proteins destined for the nucleus
KKKRK signal sequence
37
Translocation signal for proteins destined for the peroxisomes
C-terminal SKL signal sequence
38
Translocation signal for proteins destined for the ER lumen
C-terminal KDEL retention signal K - lysine D - aspartic acid E - glutamic acid L - leucine
39
Translocation signal for proteins destined for lysosomes
Mannose-6-phosphate signal group Disease: I-cell disease
40
Translocation signal for proteins destined for secretion
Tryptophan-rich domain signal region absence of retention motifs
41
Translocation signal for proteins destined for the membrane
N-terminal apolar region (stop transfer sequence)
42
Each protein in the secretory pathway has what
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
Signal recognition particle (SRP)
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
I-cell disease
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
Chaperones
Protects large proteins and helps them fold into proper tertiary structure Ex: HSP70 (uses ATP)
46
Chaperonins
Have barrel shaped compartments that admit unfolded proteins and catalyze their folding in an ATP dependent manner Ex: HSP60 (uses ATP)
47
How does proteolytic cleavage work
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
Acetylation - what type of linkage - functional group - where does it get the functional group - happens to what amino acid post translationally
Covalent linkage to amine Amine (-NH3+) Acetyl CoA Lysine
49
O-Glycosylation - what proteins - Functional group - happens to which amino acids post translationally
extracellular proteins (cell surface and plasma proteins) Hydrolysis (-OH) Serine, threonine
50
N-glycosylation - what proteins - functional group - happens to which amino acids post translationally
extracellular proteins Acid-amine (-CONH2) Asparagine
51
Phosphorylation - linkage - functional group - happens to which amino acids post translationally - what is the purpose
Ester bond between phosphate and -OH of AA Hydroxyl (-OH) Serine, tyrosine, threonine - also aspartate, histidine regulates enzyme activity, protein function, cell growth
52
Disulfide bonds - linkage - functional group - happens to which amino acids post translationally - where does this occur - facilitated by
``` Oxidation —> covalent linkage of cysteine residues Sulfhydryl (-SH) Cysteine ER lumen protein disulfide isomerases ```
53
Disulfide bonds in post translational modification
Form between thiol (SH) group of 2 cysteine residues Occurs in the ER lumen
54
Protein disulfide isomerases
Facilitates disulfide bond formation in post translational modification of proteins
55
Ehlers-Danlos Syndrome
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
Epidermolysis Bullosa Symplex
Defect in lysyl hydroylase; cannot form collagen correctly Blisters on skin
57
How does Alzheimer’s disease form
Misfolding/aggregation of amyloid beta peptide (AB) that forms plaques in the brain WITH hyperphosphorylation of Tau (microtubullary stimulating agent)
58
Sporadic form cause versus familial form cause of AD
Familial: mutations in APP (Amyloid precursor protein) and Tau Sporadic: brain aging
59
How is Parkinson’s caused
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
Familial form of PD versus sporadic form
Familial: mutations in AS (a synuclein) Sporadic: brain aging
61
How is Huntington’s disease caused
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
How is Creutzfeldt-Jacob disease caused
Misfolding of prion proteins It’s a type of transmissible spongiform encephalopathies
63
missense mutation
changes amino acid
64
frameshift mutation
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
aminoacyl tRNAs
tRNA + amino acid catalyzed by aminoacyl tRNA synthetase
66
what forms during initiation of translation (3 things)
formation of 1) mRNA, 2) small ribosomal subunit, and 3) initiator tRNA pre-initiation complex
67
what are the three stop codons
UAA UAG UGA
68
what does the release factor do
cleaves ester bond between C terminus of polypeptide and the tRNA catalyze the addition of water instead of an AA
69
HSP60
heat shock protein 60 chaperonin; folds large proteins
70
what is essential for activity of lysyl and prolyl hydroxylase
ascorbic acid

MCM Exam II (14 decks)

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