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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

22
Q

Ribosomal subunits of Euks

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
Energy requirement for Termination
Hydrolysis of 1 GTP
26
Protein Destinations in Cytoplasmic pathway
Cytosol Mito Nucleus Peroxisomes
27
Protein Destinations in Secretory pathway
ER Lysosomes PM Secretion
28
Where does protein synthesis begin and end in the Cytoplasmic pathway?
Begins & ends on free ribosomes in the cytoplasm
29
Where does protein synthesis begin and end in the Secretory pathway?
Translation begin on free ribosomes | Terminates on ribosomes sent to the ER
30
Signal for proteins --> Cytoplasm
No translocation signal
31
Signal for proteins --> Mito
N-terminal hydrophobic alpha-helix | Chaperone HSP 70 prevents protein degradation as it passes through TOM and TIM
32
Signal for proteins --> Nucleus
Small proteins pass through nuclear pores Large proteins have nuclear localization signals that have 4 continuous basic residues (Lys Arg rich; KKKRK)
33
Signal for proteins --> Peroxisome
C-terminal SKL | Serine-Lysine-Leucine
34
Signal for proteins retained in ER
C-terminal KDEL | Lys-Asp-Glu-Leu
35
Signal for proteins --> PM
Apolar region in N-terminus of the polypeptide, serves as a stop translation sequence (stop trsf).
36
Signal for proteins --> Lysosome
Mannose-6-Phosphate
37
Signal for proteins --> Secretion
Trp rich domain Absence of retention signals
38
Chaperones
Protects protein and help fold into proper 3˚ structure HSP70
39
Chaperonins
Barrel shaped compartments that admit unfolded proteins HSP60 Folding is ATP-dependent
40
Post-translational modifications (4)
Glycosylation Phosphorylation Disulfide bond formation Acetylation
41
Acetylation
Covalent linkage to amine Functional group: Amine (-NH3+) Residue affected: Lys Acetyl CoA = donor Histones regulated by acetylation (HAT & HDAC)
42
Glycosylation
O-glycosylation Functional group: Hydroxyl (-OH) Residue affected: Ser, Thr N-glycosylation Functional group: Acid-amide (-CONH2) Residue affected: Asn, Gln
43
Phosphorylation
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
Disulfide bonds
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
Alzheimer's Disease (AD)
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
Parkinson's Disease (PD)
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
Huntington's Disease (HD)
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
Creutzfeldt-Jakob Disease (HD)
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
Peptididyl transferase
Housed in large subunit
50
Post-translational modifications of Collagen
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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