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MCM I > Functions & Dysfunctions of Protein Processing > Flashcards

Functions & Dysfunctions of Protein Processing Flashcards

1
Q

Start Codon

A

AUG

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2
Q

Stop Codons

A

UAA
UAG
UGA

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3
Q

Silent Mutation

A

New codon –> same aa

Effect on protein: None

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4
Q

Missense Mutation

A

New codon –> new aa

Effect on protein: Variable

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5
Q

Nonsense Mutation

A

New codon –> stop codon

Effect on protein: Nonfunctional

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6
Q

Frameshift Mutation

A

1+ nucleotides are deleted or inserted

Effect on protein: Nonfunctional

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7
Q

Sickle Cell Anemia

A

Missense mutation of 6th codon in allele gene for human ß-globin (HBB)

GAG –> GTG
Glu –> Val

Aggregation of mutant HbA forms rigid, rod-like structures
RBC shape –> sickle-shape
Poor oxygen capacity & clog capillaries

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8
Q

Duchenne Muscular Dystrophy

A

Large in-frame & out-of-frame deletions to dystrophin gene –> partially or non-functioning dystrophin gene

OOF deletions –> little/no expression of dystrophin protein –> severe form Duchenne Muscular Dystrophy (DMD)

Muscle wasting
Confinement to wheelchair by age 12, symptoms onset by 3-5 yrs.
Death by respiratory failure within 10 yrs

In frame deletions –> truncated forms of dystrophin –> milder form Becker muscular dystrophy (BMD)
Muscle replaced with fat & fibroid, elevated CK

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9
Q

General structure of tRNA

A

Cloverleaf 2˚ structure
2 regions of unpaired nucleotides:

Anticodon loop that recognizes codon

3’ CCA terminal region which binds to aa

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10
Q

Structure of Aminoacycl tRNAs

A

aa esterfied to CCA sequence at 3’-end of cognate tRNA
aa needs to be “activated”
Each aa has it’s own amino acyl tRNA synthetase
Aminoacyl tRNA synthetases serve as second genetic code
Each tRNA charged with correct aa to maintain fidelity of protein synthesis

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11
Q

Streptomycin

A

Prok
Affects Initiation
Binds to 30S (small) ribosomal subunit

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12
Q

Tetracycline

A

Prok
Affects elongation
Binds to 30S (small) ribosomal subunit

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13
Q

Shiga toxin

A

Euk
Affects elongation
Binds to 60S (large) ribosomal subunit

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14
Q

Ricin

A

Euk

Affects elongation

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15
Q

Puromycin

A

Prok & Euk

Affects elongation

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16
Q

Chloramphenicol

A

Prok & Mito

Affects elongation

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17
Q

Cyclohexamide

A

Euk

Affects elongation

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18
Q

Clindamycin

A

Prok
Affects elongation
Binds to 50S (large) ribosomal subunit

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19
Q

Erythromycin

A

Prok
Affects elongation
Binds to 50S (large) ribosomal subunit

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20
Q

Diptheria toxin

A

Euk
Affects elongation
Inacivates EF2-GTP

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21
Q

Ribosomal subunits of Proks

A

30S

50S

22
Q

Ribosomal subunits of Euks

A

40S

60S

23
Q

Energy requirement for Initiation

A

Hydrolysis of 1 GTP

24
Q

Energy requirement for Elongation

A

Hydrolysis of 2 GTP per aa added

25
Q

Energy requirement for Termination

A

Hydrolysis of 1 GTP

26
Q

Protein Destinations in Cytoplasmic pathway

A

Cytosol
Mito
Nucleus
Peroxisomes

27
Q

Protein Destinations in Secretory pathway

A

ER
Lysosomes
PM
Secretion

28
Q

Where does protein synthesis begin and end in the Cytoplasmic pathway?

A

Begins & ends on free ribosomes in the cytoplasm

29
Q

Where does protein synthesis begin and end in the Secretory pathway?

A

Translation begin on free ribosomes

Terminates on ribosomes sent to the ER

30
Q

Signal for proteins –> Cytoplasm

A

No translocation signal

31
Q

Signal for proteins –> Mito

A

N-terminal hydrophobic alpha-helix

Chaperone HSP 70 prevents protein degradation as it passes through TOM and TIM

32
Q

Signal for proteins –> Nucleus

A

Small proteins pass through nuclear pores

Large proteins have nuclear localization signals that have 4 continuous basic residues (Lys Arg rich; KKKRK)

33
Q

Signal for proteins –> Peroxisome

A

C-terminal SKL

Serine-Lysine-Leucine

34
Q

Signal for proteins retained in ER

A

C-terminal KDEL

Lys-Asp-Glu-Leu

35
Q

Signal for proteins –> PM

A

Apolar region in N-terminus of the polypeptide, serves as a stop translation sequence (stop trsf).

36
Q

Signal for proteins –> Lysosome

A

Mannose-6-Phosphate

37
Q

Signal for proteins –> Secretion

A

Trp rich domain

Absence of retention signals

38
Q

Chaperones

A

Protects protein and help fold into proper 3˚ structure

HSP70

39
Q

Chaperonins

A

Barrel shaped compartments that admit unfolded proteins

HSP60

Folding is ATP-dependent

40
Q

Post-translational modifications (4)

A

Glycosylation
Phosphorylation
Disulfide bond formation
Acetylation

41
Q

Acetylation

A

Covalent linkage to amine

Functional group: Amine (-NH3+)

Residue affected: Lys

Acetyl CoA = donor
Histones regulated by acetylation (HAT & HDAC)

42
Q

Glycosylation

A

O-glycosylation
Functional group: Hydroxyl (-OH)
Residue affected: Ser, Thr

N-glycosylation
Functional group: Acid-amide (-CONH2)
Residue affected: Asn, Gln

43
Q

Phosphorylation

A

Phosphate linked via esterfication

Functional group: Hydroxyl (-OH)

Residue affected: Ser, Tyr, Thr; Asp, His

Regulates enzyme activity and protein function (signaling)
Cell growth, proliferation, differentiation, oncogenesis

44
Q

Disulfide bonds

A

Oxidation to achieve covalent linkage of cysteine residues

Functional group: Sulfahydryl (-SH)

Residue affected: Cys

Stabilize proteins
Facilitated by protein disulfide isomerases
Formation & recognition of bonds occur in ER lumen

45
Q

Alzheimer’s Disease (AD)

A

Amyloid precursor protein (APP) breaksdown amyloid beta peptide (Aß)

Misfolding/Aggregation Aß forms plaques in brain (extracellular)

Hyperphosphorylation of Tau (neurofibrillary tangles)

Familiar forms = Mutations in APP and Tau
Sporadic form = Brain aging

Loss of memory, cognitive function, language

46
Q

Parkinson’s Disease (PD)

A

Aggregation of alpha-synuclein (AS) protein –> insouble fibrils (Lewy bodies) in dopaminergic neurons in substantia nigra

Reduced dopamine
Death of selected neurons

Familial form = Mutations in AS
Sporadic form = Brain aging

Impairment of motor control

47
Q

Huntington’s Disease (HD)

A

Mutation in Huntington gene –> expansion of CAG triplet repeats

Polyglutamine repeats in abnormal HTT protein
Forms intramolar H-bonds –> misfold & aggregate

Selective death of cells in basal ganglia

Loss of movement, cognitive functions and psychiatric problems

48
Q

Creutzfeldt-Jakob Disease (HD)

A

Misfolding of prion proteins

Transmissible

Belongs to Transmissible spongiform encephalopathies (TSEs)

Failing memory, behavioral changes, lack of coordination and visual disturbances. Late stages involve mentral deterioration, blindness, weakness of extremities, and coma.

49
Q

Peptididyl transferase

A

Housed in large subunit

50
Q

Post-translational modifications of Collagen

A

Collagen most abundant structural protein in vertebrates
Heterotrimeric

Lysines modified –> 5-hydroxylysines, further glycosylated with glucose & galactose
Some lysines deaminated –> aldehydes
Some prolines hydroxylated –> hydroxyprolines
Modifications important for assembly of collagen

Ascorbic acid essential for activity of lysyl & prolyl hydroxylases

Defects in lysyl hydroxylases => skin, bone and joint disorders such as Ehlers-Danlos syndrome, Nevo syndrome, Bruck syndrome, Epidermolysis Bullosa Simplex

Ehlers Danlos Syndrome- Overly flexible joints, walls of blood vessels, intestines or uterus may rupture
Epidermolysis Bullosa Simplex - Blisters on skin

MCM I (6 decks)

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