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Biochem > Translation and Protein Processing > Flashcards

Translation and Protein Processing Flashcards

1
Q

Purpose of Kozak sequence in mRNA strand?

A

Ribosomal binding during translation

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2
Q

Subunits of eukaryotic 80S ribosome?

A

60S and 40S subunits

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3
Q

Proteins assoc w/ polyribosomes on RER surface are cotranslated where?

A

Thru RER membrane into ER lumen

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4
Q

What marks start of translation initiation?

A

mRNA binds 40S ribosomal subunit

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5
Q

What marks start of elongation?

A

60S subunit binds to complex and forms active ribosome

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6
Q

Function of eIF2?

A

Facilitates binding of initiating Met-tRNA(Met) to 40S subunit

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7
Q

Functions of eIF3? (2)

A
  • First factor to bind 40S subunit

- facilitates subsequent steps

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8
Q

Functions of eIF4A? (2)

A
  • RNA helicase activity removes secondary structure in mRNA to permit binding to 40S subunit
  • part of eIF4F complex
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9
Q

Functions of eIF4B? (2)

A
  • binds to mRNA

- facilitates scanning of mRNA to locate first AUG

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10
Q

Cause of CNS Hypomyelination and Vanishing White Matter (VWM)?

A

Missense mutation in eIF2

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11
Q

Direct effort of VWM?

A

Decreased expression/function of eIF2

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12
Q

Mechanism of VWM and fever? (4)

A
  • translation often stalled in response to stress (eg fever)
  • eIF2 prevents accumulation of misfolded proteins by preventing translation during fever
  • eIF2 mutation impairs this ability
  • abnormal folded proteins build up and affect glial cells –> loss of myelin sheath
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13
Q

Mechanism of tetracycline?

A
  • bacterial antibiotic

- inhibits binding of aminoacyl-tRNA @ A-site

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14
Q

Mechanism of chloramphenicol?

A
  • bacterial antibiotic

- inhibits peptide bond formation by Peptidyltransferase

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15
Q

What powers translocation?

A

GTP hydrolysis bound to eEF-2 translocase

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16
Q

What bacterial antibiotic inhibits translocation?

A

Erythromycin

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17
Q

Functions of eIF3 and eIF6?

A
  • eIF3 binds inactive 40S subunit until next intitiation

- eIF6 binds 60S subunit

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18
Q

Functions of Streptomycin? (2)

A
  • prevents transition from initiation complex to chain elongation
  • causes miscoding
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19
Q

Function of Rifamycin?

A
  • blocks transc initiation by binding RNA Pol
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20
Q

Function of heat shock proteins?

A
  • prevent inappropriate hydrophobic aggregations b/w nearby AAs
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21
Q

Function of Peptidyl Prolyl cis-trans Isomerase?

A
  • converts Pro res from trans to cis config

- cis-Proline can form hairpin beta-turns

22
Q

Function of Protein Disulfide Isomerase (PDI)?

A
  • breaks inappropriate disulfide bonds until correct ones are formed
23
Q

How are Amyloidoses formed? (2)

A
  • exposed beta-sheets form aggregate w/ similarly misfolded beta-sheets –> amyloid fibrils
  • fibrils further assemble into insoluble Amyloidoses
24
Q

Mechanism of Alzheimers? (4)

A
  • Amyloid Precursor Protein (APP) should be alpha-helical
  • APP proteolytic cleavage –> misfolding into beta sheets
  • beta sheets aggregate thru Phe interactions
  • beta amyloid plaques form in extracell space
25
Q

Role of amyloid formation in Type II diabetes? (3)

A
  • improper folding of Islet Amyloid Polypeptide (IAPP, Amylin)
  • apoptosis of pancreatic beta islet cells
  • reduced amylin and insulin levels
26
Q

Role of amyloid formation in Huntigton’s disease? (4)

A
  • misfolding of Huntingtin (HTT) protein –> aggregates
  • HTT has 5’-CAG-3’ tri-nt repeats that code for polyQ res chain
  • more than 40 res –> full disease penetrance
  • mutant HTT cleaved and yields amyloid aggregates that interfere w/ NT release
27
Q

Role of amyloid formation in Parkinson’s disease? (2)

A
  • aggregates from misfolding of alpha synuclein (Lewy bodies)
  • results in death of dopaminergic neurons
28
Q

Role of amyloid formation in Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig’s disease)? (2)

A
  • affects motor neurons
  • Superoxide dismutase protein (SOD1) becomes misfolded –> aggregates
  • only accts for a small fraction of ALS cases
29
Q

Role of amyloid formation in Spinal cerebellar ataxia? (3)

A
  • Ataxin protein has CAG tri-nt repeats
  • promotes stretch of PolyQ res
  • also non-polyQ mediated mechanisms
30
Q

What enzymes cleave APP to produce PM protein? (2)

A
  1. alpha secretase cleaves APP in extracell domain
  2. gamma secretase (Presenelin, PSEN1) cleaves APP in intracell domain
    - leaves non-harmful 26 res peptide embedded in PM
31
Q

Discuss dvp’ment of beta amyloid plaque (3)

A
  • beta secretase cleaves APP in a diff extracell location
  • generates 42 res peptide (AB42)
  • has more beta strand structure that misfolds and aggregates
32
Q

Characteristics of Familial Alzheimer’s disease (FAD)? (2)

A
  • early onset of symptoms and accelerated progression

- mutation w/i APP seq that cluster near AB42 and enchance proteolysis –> more AB42 production

33
Q

Genetic components of late onset Alzheimer’s disease? (5)

A
  • involves Apolipoprotein E (ApoE)
  • involved in transprt of cholesterol- and TGC-carrying complexes in blood
  • homozygous E4/E4 ind’s have higher risk for Alzheimer’s
  • homozygous E2/E2 may be protective for Alzheimer’s
  • E3 allele has no seen effect
34
Q

Clinical importance of acylation? (2)

A
  • occurs b/w palmitate or myristate and proteins on cytosolic leaflet of PM
  • Src (proto-oncogene kinase) becomes oncogenic after acylation
35
Q

Clinical importance of prenylation? (4)

A
  • occurs b/w unsat FA farnesyl or geranylgeranyl and proteins on C-leaflet of PM
  • Ras proto-oncogene is prenylated normally
  • loss of prenylation –> decrease in Ras oncogenic transformation
  • cancer drugs inhibit Ras prenylation
36
Q

Clinical importance of GPI-linked proteins? (3)

A
  • covalenty bound to phospholipid phosphatidylinositol via series of intervening carbs
  • assoc w/ E-leaflet of PM
  • involved in blood coagulation cascade
37
Q

How is acetylation used for (acetylsalicylic acid) Aspirin delivery?

A
  • it makes molec’s more permeable to blood-brain barrier (BBB)
38
Q

What important signaling molec is tri-methylated?

A

Calmodulin

39
Q

Mechanism of blood clotting factor Prothrombin? (2)

A
  • contains gamma-CarboxyGlu res for neg charge

- neg charge helps it effectively bind Ca2+

40
Q

What does a Prothrombin time (PT) measure?

A

Blood coagulation

41
Q

Explain why breast milk supplies AA, phosphate, and Ca2+? (2)

A
  • casein is main milk protein

- contains many phosphoserine res that bind Ca2+

42
Q

Describe insulin cleavage (4)

A
  • PreProinsulin has its N’ end cleaved in ER
  • disulfide bonds formed in oxidizing env of ER –> Proinsulin
  • internal C-peptide cleaved off Proinsulin
  • A chain and B chain held together by disulfide bonds –> final insulin protein
43
Q

What is precursor peptide for several peptide NTs?

A

Propiomelanocortin (POMC)

44
Q

Components of holoenzyme? (2)

A
  • active enzyme

- coenzyme prosthetic group

45
Q

What is an apozyme (apoprotein)?

A

Inactive enzyme w/o its prosthetic group

46
Q

What peptide res receives Ub tag?

A

Lysine

47
Q

Enzyme that does Ub taggin?

A

Ub-ligase

48
Q

Where do polyubiquinated proteins go?

A

26S proteasome complex

49
Q

Composition of ricin? (2)

A
  1. B chain w/ galactose binding chains that allows cell entry thru H-bonding
  2. A chain = active site that depurinates adenine bases w/i rRNA
50
Q

Mechanism of ricin poisoning? (3)

A
  • depurinates adenine bases w/i 28S rRNA
  • depurinated 28S rRNA targeted for degradation
  • inhibits translation
51
Q

Most important posttranscriptional modification of tRNA?

A

Addition of CCA seq to 3’ end of molec

Biochem (9 decks)

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