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MCM Quiz2 > Functions and Dysfunctions of protein processing > Flashcards

Functions and Dysfunctions of protein processing Flashcards

1
Q

component of Prokaryotic ribosome?

A

70S large subunit & 30S small subunit

50S

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2
Q

component of Eukaryotic ribosome?

A

60S large subunit & 40S subunit

80 S total

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3
Q

Three component of ribosomes?

A

Acceptor (A site)

Peptidyl (P Site)- Aminoacyl tRNA’s attach and add AA here

Empty (Exit Site)

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4
Q

What are Aminoacyl tRNAs? where do they attach to AA?

A

Complex of tRNA w/ AA

AA esterified to CCA terminal region at 3’ end of tRNA

CCA terminal region binds AAs that match corresponding codon

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5
Q

what is used to activate AA?

A

Aminoacyl tRNA synthetase, each AA has own

Charged with correct AA to maintain fidelity of protein synthesis

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6
Q

Two steps in AA activation?

A

Aminoacyl tRNA synTHETASE catalyzes addition of AMP to COOH end of AA

AA transferred to cognate tRNA

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7
Q

Three steps of AA synthesis?

A

Initiation

Elongation

Termination

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8
Q

Steps in initiation of translation?

A

In Eukaryotes initiation occurs in the Kozak sequence and an ATP-dependent mRNA scan

  1. First AA (MET) binds to P site on small ribosomal subunit, eukaryotic initiation factor (eIF2) binds to GTP
  2. mRNA slides across small subunit until AUG is found
  3. eIF2 and other initiation factors dissociate
  4. Large ribosomal subunit binds
  5. As ribosome complex slides across mRNA, the next Aminoacyl tRNA is recruited
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9
Q

Steps in elongation of translation?

A

Activated AA attached to initiating MET by
forming a peptide bond

  1. Loading of an Aminoacyl tRNA onto the ribosomes such that the anticodon bases pairs with codon positioned on “A Site”
  2. Prior to loading, the Aminoacyl tRNA is attached to a GTP-bound elongation factor
  3. Loading accompanied by GTP hydrolysis and release of factor from Aminoacyl tRNA
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10
Q

Steps in elongation of termination?

A
  1. Termination triggered by stop codons
  2. Stop codons are recognized by release factors (RFs)
  3. RFs bind to “A” ste and cleaves the ester bond between C terminus of polypeptide of tRNA
  4. GTP hydrolysis dissociates ribosomal complex
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11
Q

Streptomycin, what does it do?

A

binds to 30S subunit to disrupt initiation of translation

in prokaryotes

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12
Q

Clindamycin & Erythromycin, what do they do?

A

bind to 50S subunit to disrupt translocation of ribosome

in prokaryotes

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13
Q

Shiga Toxin & Ricin

A

binds to 60S subunit to disrupt elongation in eukaryotes

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14
Q

Diphtheria toxin

A

inactivates EF2-GTP and inhibits elongation

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15
Q

Tetracyclines?

A

bind to the 30S subunit to disrupt elongation

Blocks aminoacyl-tRNA to ribosomal complex

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16
Q

Puromycin?

A

causes premature chain termination in both prok/euks

Forms a puromyclated chain at 3’ end of aminoacylated-tRNAs which leads to premature chain release

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17
Q

Chloramphenicol

A

inhibits peptidyl transferase in prokaryotes

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18
Q

Cycloheximide

A

inhibits peptidyl transferase in eukaryotes

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19
Q

Sickle cell anemia, what does it do?

A

Change in 6th codon of GAG to GTG changing VAL(hydrophobic/ mutant) from GLU(negatively charged and hydrophilic/ wild type)

Deformed RBC have poor oxygen capacity and clog capillaries, restricting blood flow

missense

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20
Q

Duchenne muscular dystrophy, what is it do?

A

Large out-of-frame deletion that causes a non-functioning dystrophin gene

In-frame deletion results in expression of truncated forms of dystrophin

21
Q

What are the two protein sorting pathways?

A

Cytoplasmic

Secretory

22
Q

Where do proteins in te cytoplasmic sorting pathway go?

A

have no translocation signals

cytosol, mitochondria, nucleus, and peroxisomes

23
Q

How does translation in the cytoplasmic pathway work?

A

Translation begins and ends on free ribosomes

24
Q

N terminal hydrophobic A-helix signal ? where does it go?

A

peptide goes to mitochondria

25
Q

LYS, ARG rich , where does it go?

A

nucleus

26
Q

-SKL, where does it go?

A

peroxisome

27
Q

How do proteins get to the mitochondria?

A

TIM and TOM

28
Q

What are nuclear localization signals?

A

help large molecules go in nucleus

KKKKRK

29
Q

Where do proteins in the secretory pathway go?

A

ER, lysosomes, plasma membrane, or for secretion

30
Q

where does translation in the secretory pathway happen?

A

Translation begins on free ribosomes, but ends on ribosomes sent to ER

31
Q

Whats special about secretory pathway structures?

A

First 20 AA residues of polypeptide has ER targeting signal sequences

15-60 AA at N terminus of protein
1-2 basic AA near N terminus

Followed by Extremely hydrophobic sequence on C terminus of the basic residues

32
Q

How do proteins get into ER lumen

A

Signal recognition particle (SRP) binds to ER-targeting signal and ribosome during translation

Wraps itself around ribosome-mRNA-peptide complex, tethering it to ER membrane halting translation temporarily

Resumes when protein directed into ER lumen trough translocator

Enzymes on luminal side cleave the signal to release the protein

Protein undergoes post-translational modification in ER and/or golgi

33
Q

KDEL?

A

ER lumen proteins

34
Q

Mannose-6-phosphate?

A

for lysosomal proteins

ICELL DISEASE!!

35
Q

tryptophan rich domains?

A

proteins for secretion

36
Q

N terminal apolar regions?

A

proteins for membranes

37
Q

I-cell disease, what is it?

A

Tagging of proteins with mannose 6P is broken

Severe form of lysosomal storage disease

High plasma levels of lysosomal enzymes
@6mo FTT & developmental delays and physical manifestations

Hepatomegaly, splenomegaly, occasional heart valve damage

Developmental delays, motor function delays, and more pronounced cognitive delays

38
Q

Chaperonins? what do they do?

A

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

large proteins cant fold on their own

39
Q

what is Glycosylation? significance?

A

Addition of sugar residues to proteins

O-linked: occurs through hydroxyl groups of serine / threonine residues

N-linked: occurs through asparagine residues (N-H bonds)

too much=cataracts

40
Q

what is Phosphorylation ? significance?

A

Formation of an ester bond b/w phosphate and OH

Via serine/threonine and tyrosine kinase
Regulates enzyme activity and protein function

41
Q

what is Disulfide bond formation? significance?

A

S-S bonds between cysteines, allows for tertiary structure for proteins

42
Q

what is Acetylation ? significance?

A

Covalent linkage to amine, LYSINE

Use acetly cOa as donor

Catalyzed by HAT

Histone modifications are heritable

43
Q

what is significance of Post-translational modifications of collagen?

A

Collagen most abundant structural protein in vertebrates

Lysines in collagen modified to form 5-hydroxylysine, further glycosylated with addition of glucose or galactose

Ascorbic acid essential for activity of lysl and prolyl hydroxylases

44
Q

Defects in lysyl hydroxylases result in?

A

Ehlers-Danlos- overly flexible joints, walls of blood vessels, intestines or uterus may rupture

45
Q

Alzheimers, what is it, how does it happen?

A

loss of memory, cognitive function

Amyloid beta peptide: plaques formed

Tau is hyperphosphorylated (TANGLES!)

APP and Tau cause familial forms of AD

46
Q

PArkinsons, what is it , how does it happen?

A

fine motor control doesnt work

A synuclein undergoes deposition as Lewy bodies

Reduced availability of dopamine

Aging causes sporadic form

47
Q

Huntington,what is it , how does it happen?

A

loss of movement, cognitive functions, psychiatric problems

Huntingtin gene mutation: CAG triplet repeats

Polyglutamine repeats

Death of cells in basal ganglia

48
Q

Creuzfeld, what is it , how does it happen?

A

transmissable, behavioral changes, lack of coordination, mental deterioration
prions!

MCM Quiz2 (10 decks)

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