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MCM > Zaidi, Protein Processing > Flashcards

Zaidi, Protein Processing Flashcards

1
Q

Start Codon

A

AUG, Methionine

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2
Q

Stop Codons

A

UAA, UAG, UGA

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3
Q

Silent Mutation

A

new codon, no change in AA, no effect on protein

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4
Q

Missense Mutation

A

new codon, a change in the AA, variable effect
if a similar AA: no effect on protein
if a different AA: changes protein effect (sickle cell anemia)

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5
Q

Nonsense Mutation

A

new codon, changes into a stop codon, nonfunctional protein

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6
Q

Frameshift Mutation

A

1+ nucleotide added/deleted, creates nonfunctional protein (duchenne muscular dystrophy)

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7
Q

Sickle Cell Anemia

A

missense mutation of 6th codon in allele for human beta global (HBB)

changes Glu into a Val (go from negatively charged and hydrophilic to neutral and hydrophobic)

HbA aggregates in rod-like structure, deforms RBC’s, poor oxygen capacity and clog capillaries

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8
Q

Duchenne Muscular Dystrophy

A

deletions of dystrophin gene leads to partial or non-functioning dystrophin protein
Frameshift mutation

Out of frame (OOF) causes little to no expression of protein and cause severe form of DMD

in frame results in truncated forms of protein and is milder (Becker MD)

sx: muscle wasting, death by resp. failure by 10yo

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9
Q

mRNA

A

has codons for AA

after transcription pre-mRNA into mRNA and then goes to cytoplasm for translation

7-methylguanosine (5’ cap) & Poly(A) tail

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10
Q

tRNA

A

adaptors, transfer AA to ribosome for synthesis
match AA to codons in mRNA

anticodon loop- pair with complementary codon
3’CCA terminal region- binds the AA that matches

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11
Q

Codons

A

sequence of 3 bases that signal for a protein

64 possibilities, 3 stop codons, 1 start codon,

61 triplet codons for 20 AAs

degenerate- some AA have multiple sequences

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12
Q

Aminoacyl tRNA synthetase

A

catalyzes addition of AMP to COOH to activate the AA

each AA has its own aminoacyl tRNA synthetase

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13
Q

Ribosomes

A

translation occurs here!
large and small subunit (eukary- 30s & 50s, prokary- 40s & 60s)

Acceptor site (A)- mRNA codon exposed to receive aminoacyl tRNA, new tRNA comes in

Peptidyle site (P)- aminoacyl tRNA attaches here

Empty/Exit site (E)- empty tRNA before exiting ribosome,

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14
Q

Translation

A

•Translation occurs in the 5’ to 3’ direction
3 steps:
1. Initiation: formation of mRNA, small ribosomal subunit and initiator tRNA pre-initiation complex
2. Elongation: activated AA attached to initiating Met by forming a peptide bond
3. Termination: peptide chain released

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15
Q

Translation, Initiation

A

Protein synthesis begins

requires 1 GTP

Initiator tRNA = methionyl tRNA, which is bound to GTP is attached to P site on the Small su

other eIF’s are added
the Large su is added once the eIF’s and GTP fall off and are removed

translation begins with the initiation codon AUG (code for Met)

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16
Q

eIF’s

A

eukaryotic initiation factors

**see this, think translation initiation

17
Q

Translation, Elongation

A

Requires 2 GTP for every AA attached

Aminoacyl tRNA (attached to GTP bound elongation factor-EF) binds with next AA at the A site

2 AA (Met and next one) attached via peptide bond catalyzed by peptide transferase

continued cycle

18
Q

Translation, Termination

A

Peptide chain released and ribosomal complex dissociates

requires 1 GTP

triggered by stop codons (UGA, UAA, UAG)

stop codons recognized by Release Factors (RFs) which bind to the A site, and cleave the ester bond between C-terminus and the tRNA

GTP hydrolysis dissociates ribosome complex

19
Q

Inhibitors of Translation

A

Streptomycin-disrupts initiation, bind to 30s

Clindamycin; erythromycin- disrupt translocation and thus elongation, bind to 50s

Tetracyclines- disrupt elongation, bind 30s

More elongation disruptors:

  • shiga toxin-bind 60s
  • ricin
  • puromycin
  • diptheria toxin- bind EF2-GTP
  • cycloheximide
  • chloramphenicol
20
Q

Cytoplasmic pathway

A

proteins destined for:

  • cytoplasm
  • mitochondria: N terminal hydrophobic alpha-helix
  • nucleus: KKKRK
  • peroxisome: SKL
21
Q

Secretory pathway

A

protein sorting, trafficked via vesicles

  • membrane: N terminal apolar (stop tsrf)
  • lysosome: Mannose 6-P
  • secretory vesicle: Trp rich domain
  • stay in ER: KDEL
22
Q

Mitochondria transport & Cytoplasmic Pathway

A

proteins get help from chaperone proteins (heat shock family, hsp) which protect the protein in it’s linear form as it passes through membrane

TOM-Transporter in outer membrane
TIM- Transporter in inner membrane

chaperone: HSP70

23
Q

Signal recognition particle (SRP)

A
  • binds to ER-targeting signal, wraps around ribosome-mRNA-peptide complex and halts translation
  • binds to SRP receptor on ER membrane
  • resumes translation when protein is put into the ER lumen
  • enzymes inside of membrane cleave signal (SRP)
24
Q

Post-translational processing; protein folding

A
  • small proteins have no problem
  • large proteins are at risk for damage and thus need chaperons and chaperonins (use ATP)
  • chaperone = HSP70 -chaperonin = HSP60
25
Q

Post-translation processing; proteolytic cleavage

A

converts inactive to active enzymes by unmasking active site (zymogens into enzymes)

trypsinogen into trypsin
chymotrypsinogen into chymotrypsin

converts precursor proteins into mature
(proinsulin into insulin)

26
Q

Glycosylation

A

O-linked: uses Ser or Thr residues for hydroxyl groups

N-linked: uses Asn only for amino group

Cell recognition, ID, protection

27
Q

Phosphorylation

A

formation of an ester bond between phosphate and OH

uses serine/threonine and tyrosine kinase

phosphate removed by phosphatases

regulates enzyme activity and protein function
also: cell growth, proliferation, differentiation, and oncogenesis

28
Q

Disulfide bonds

A

inter and intra-molecular disulfide bonds formed to stabilize proteins

between thiol (SH) groups from 2 cysteines and facilitated by protein disulfide isomerases

occurs in ER lumen

29
Q

Acetylation

A

typically acetylated on lysine residues

Acetyl comes from Acetyl CoA

Histones acetylated/deacetylated for gene regulation

Histone acetyltransferase (HAT), increase transcription

Histone deacetylase (HDAC), halt transcription

histone modifications are inheritable (epigenetics)

30
Q

Post-translational Modification of Collagen

A

most abundant structural protein, heterotrimeric

ascorbic acid essential for lysyl and prolyl hydroxylates

defect in lysyl hydroxyls results in skin, bone, & joint disorder

ex: Ehlers-Danlos syndrome: over flexible joints, walls of blood vessels, intestines, or uterus may rupture
ex: epidermolysis bullosa simplex- skin blisters

31
Q

Alzheimers Disease

A
  • Amyloid precursor protein (APP) breaks down and forms amyloid beta peptide (Abeta)
  • misfolding of Abeta causes plaque formation in brain

hyperphosphorylation of Tau (neurofibrillary tangles)

Sx: memory loss, cognitive fx, lagnuage

32
Q

Parkinsons Disease

A

alpha-synuclein (AS) protein causes Lewy bodies in dopaminergic neurons in substantia nigra

results in decrease in dopamine

Sx: impaired fine motor control

33
Q

Huntington’s Disease

A

mutation in huntingtin gene results in CAG repeats

results in polyglutamine repeats, leads to misfolding/aggregation

selective death of cells in basal ganglia

Sx: loss of movement and cognitive functions

34
Q

Creutzfeldt-Jacob Disease

A

misfolding of prion proteins

transmissible disease, causes other proteins to misfiled

Transmissible spongiform encephalopathies (TSE’s)

Sx: failing memory, behavioral changes, lack of coordination, etc

MCM (6 decks)

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