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SFM > (L12) Functions and Dysfunctions of Protein Processing > Flashcards

(L12) Functions and Dysfunctions of Protein Processing Flashcards

1
Q

What are the ribosomal subunits in prokaryotes and eukaryotes?

L12 S14

A

Prokaryotes:

  • 30S
  • 50S

Eukaryotes

  • 40S
  • 60S
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2
Q

What is the mechanism of streptomycin?

L12 S15

A

Binds to 30S subunit (prokaryotic) and interferes with binding to fmet-tRNA, preventing initiation.

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3
Q

What is the mechanism of clindamycin and erythromycin?

L12 S15

A

Binds to 50S subunit (prokaryotic) blocking translocation of ribosome.

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4
Q

What is the mechanism of tetracycline?

L12 S15

A

Binds to 30S subunit (prokaryotic) blocking binding of aminoacyl-tRNA, preventing elongation.

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5
Q

What is the mechanism of chloramphenicol?

L12 S15

A

Binds 50S subunit (prokaryotic) and inhibits peptidyl transferase activity, preventing peptide bond formation.

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6
Q

What is the mechanism of shiga toxin and ricin?

L12 S16

A

Binds to 60S subunit (eukaryotic) preventing binding of aminoacyl-tRNA preventing elongation.

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7
Q

What is the mechanism of diphtheria toxin?

L12 S16

A

Binds elongation factor-2 interfering with ribosomal translocation (eukaryotic)

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8
Q

What is the mechanism of cycloheximide?

L12 S16

A

Inhibits peptidyl transferase activity, preventing peptide bond formation. (Eukaryotic)

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9
Q

What is the mechanism of puromycin?

L12 S17

A

Mimics 3’ end of tRNA and causes premature terminations. Stops functioning of ribosome. (euk/prok)

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10
Q

What are the types of mutations and what occurs with each type?

L12 S20

A

Silent:

-no change in amino acid

Missense:

  • change in amino acid
  • can have no function effect on protein or significant functional effect

Nonsense:

-creates stop codon

Frameshift:

-addition or removal of an nucleotide causing shift of codons resulting in completely different amino acid sequence

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11
Q

What is Sickle cell anemia and what sort of mutation leads to it?

L12 S21

A

Caused by a missense mutation of β-globin gene. Sixth codon goes from GAG (Glu, acidic) to GTG (Val, hydrophobic).

Leads to aggregation of hemoglobin creating sickle shaped RBCs with diminished oxygen carrying capacity.

-Tends to clog capillaries.

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12
Q

What is Duchenne muscular dystrophy and what sort of mutation leads to it?

L12 S22

A

Caused by an out-of-frame deletion that results in massive loss of function of dystrophin gene.

Inframe deletions: result in expressions of truncated forms of dystrophin giving rised to beker muscular dystrophy.

Results in muscle wasting beginning at age of 3-5 leading to being wheelchair bound by the age of 12 with death in 10 years due to respiratory failure.

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13
Q

What are the major pathways of protein sorting? What organelles are the proteins going to?

Where are the ribosomes located?

L12 S25

A

Cytoplasmic:

  • proteins for cytosol, mitochondria, nucleus, or peroxisome
  • ribosomes are free in the cytosol

Secretory:

  • proteins for ER, lysosomes, plasma membrane, or secretion
  • ribosomes attached to ER
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14
Q

What signals target proteins for cytoplasm, mitochondria, nucleus, peroxisome, ER lumen, lysosome, or secretion?

L12 S27-28

A

Cytoplasm: no code

Mitochondria: n terminal hydrophobic α-helix

Nucleus: Lys-Arg rich

Peroxisome: c terminal - SKL

ER: c teriminal - KDEL

Lysosome: mannose 6-P

Secretion: Trp-rich

membrane: N terminal a polar region

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15
Q

What are the proteins associated with protein transport for the mitochondria (3)?

L12 S30

A

HSP70: keeps protein unfolded during transportation and prevents it from being chopped up through cytoplasm until it reaches TOM

TOM (transporter of outer membrane)

TIM (transporter of inner membrane)

As protien is moving though it HSP 70 is stripped off

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16
Q

What signal and process is common of all protiens in the secretory pathway?

L12 S33-36

A

ER-targeting signal:

  • 1-2 basic AAs followed by hydrophobic (10-15)
  • recognized by signal recognition particle (SRP) bind ribosome and halts translation
  • tetherers it to ER and facilitates insertion of protein into ER membrane during translation

ER-target signal cleaved in ER luminal side

-the protein will undergo post translational modification in ER and golgi, adiditonal signal sequence serve as guide to each protein to final destination

17
Q

What is I-cell disease and what causes it?

L12 S37

A

Results from defective tagging of lysosomal enzymes with lysosomal transport signal (mannose 6-P) and proteins are instead released outside of cell.

Leads to developmental delays, coarse facial features, restricted joint movement, failure to thrive, hepatosplenomegaly, and heart valve defects.

High plasma levels of lysozomal enzymes

Death typically by the age of 7 from CHF or respiratory tract infections.

18
Q

What mechanisms of protein folding are there and what occurs to improperly folded proteins? Where does it occur?

A

Spontaneous:

-smaller proteins

Chaperones (passive assistance):

-larger proteins

Chaperonins (active assistance): need ATP for this

-large proteins

Aggregation:

-improperly folded large proteins

OCCURS IN ER LUMEN

19
Q

How is proteolytic cleavage used as a post-translational process?

L12 S41

A

Unmasking:

-cleavage of masking sequence revealing sequence need for proper functioning

Activation of precursor:

-eg. pro[enzyme] to [enzyme]

20
Q

What are the 4 main covalent modifications of proteins? What amino acids are modified

L12 S42-43

A

Acetylation: on histones or proteins

  • addition to amine on a lysine uses actyl COA as the acetyl group doner
  • catylzed by HAT and HDAC

Glycosylation:

-addition to hydroxyl (O-glycosylation)

—Ser, Thr

-addition to acid-amine (N-glycosylation)

—Asn, Gln

precurosor sugar for n linked is phospho dolichol

Phosphorylation:

  • addition to hydoxyl
  • Ser, Tyr, Thr, Asp, and His

Disulfide:

-connection of 2 cysteines via sulfhydryl (by protien disulfide isomerases in ER lumen)

21
Q

How is collagen post-translationally modified?

L12 S50

A

Lysines and prolines are hydroxylated and then glycosylated.

This is achieved by lysyl and prolyl hydroxylases which are ascorbic acid (Vitamin C) dependent.

22
Q

What is the mechanism of Alzheimer’s disease?

What are the two types?

L12 S53

A

Familila form: mutation of APP and Tau

Misfolding of amyloid β peptide resulting in plaque formation

  • amalylod precuror protein breaks down to form amyloid beta peptide (ab) (extracellular)
  • or-

Hyperphosporylation of Tau (intra)

Sporadic:

-age related changes

23
Q

What is the mechanisms of Parkinson’s disease?

Where does it occur? What are the two types?

L12 S55

A

Aggreation of α-synuclein protein (as) forming inslouble fibers resulting in Lewy bodies. Occurs in dopaminergic neurons of substantia nigra resulting in decreased dopamine.

Familial form:

-AS mutation

Sporadic:

-age related changes

24
Q

What is the mechanism of Huntington’s disease?

Where does this occur?

L12 S56

A

Mutation of Huntingtin gene that results in increased number of CAG (glutamine) triplet repeats resulting in abnormal protein structure.

Poly gluatmine repeats form intramolecular H bonds which missfold and agregate.

Causes selective cell death in basal ganglia.

25
Q

What is the mechanism of Creutzfeldt-Jakob disease?

What is special about how this disease occurs?

L12 S57

A

Misfolded prion proteins

Misfolded proteins causes normal proteins to misfold if consumed. Misfolded proteins can be transmitted via consumption.

Belongs to transmissible spogiform encephalopathies.

26
Q

How are stuff imported in nucleus?

A

By nuclear pores

  • small protiens are able to pass though pores
  • large porteins need nuclear localization singal (lys arg)
27
Q

Defects in lysyl hydroxylases cause

A

Ehlers danlos syndrome or epidermolysis bullosa simplex

28
Q
A

SFM (31 decks)

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