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2 types of protein aggregates
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aggregate without cross-  structure
non-amyloid
ex: sickle cell anemia
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aggregate with cross- structure
amyloid
ex: Alzheimer's, Parkinson's, cataracts
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cause of sickle cell disease
single nucleotide change from GAG to GTG at amino acid position 6 (E6V) in the -chain of Hb
(charged -> hydrophobic)
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Hb S
- - sickle Hb - stick to one another forming long rod-like fibers
- - 14 sickle Hb chains twine as an
 -helical bundle
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structure of sickle cell aggregates
-helical structure
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most common cause of dementia in the elderly
Alzheimer's disease
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deposits of beta-amyloid protein generated from Alzheimer amyloid precursor protein (APP) which accumulates in spaces between nerve cells
amyloid plaques
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deposits of tau proteins involved in microtubule formation
neurofibrillary tangles
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control motility/movement of brain cells
neurofibrils
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location of APP gene
chromosome 21
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kinetics of amyloid formation
- 1) native protein unfolds -> hydrophobic residues exposed
- 2) hydrophobic patches form circular aggregates (oligomers)
- 3) oligomers stack & form protofibrils
- 4) protofibrils twine around one another & form long amyloid fibrils
- 5) fibrils precipitate -> amyloid plaques
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2 processes of amyloid growth
- 1) nucleation (lag phase)
- 2) propagation
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risk factors for AD
- 1) old age
- 2) alterations on chromosomes 1, 14, or 21
- 3) head injury
- 4) gender (more common in women)
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protein involved in Parkinson's disease
-synuclein -> becomes unfolded & forms amyloid-like filaments
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filamentous inclusions within dopaminergic neurons in Parkinson's disease
Lewy Bodies
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inherited autosomal dominant progressive neurodegenerative disease characterized by chroeiform movements, psychiatric problems, and dementia
Huntington's Disease
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peptide necessary for embryonic development, and helps with cell regulatory processes
Huntingtin peptide
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important for diagnosis, disease onset, and severity determination in Huntington's disease
number of CAG repeats in mutant Huntingtin
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what does Huntington's disease mainly attack?
basal ganglia of the brain
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most probable protein at fault for Huntington's disease
Rhes (guanine nucleotide binding protein selectively located in the striatum)
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neurodegenerative disease affecting nerve cells in the brain and spinal cord, resulting in progressive weakness of voluntary muscles and paralysis
myotropic lateral sclerosis (ALS) or Lou Gehrig's disease
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homodimer that protects cells from superoxide toxicity by converting it to water
superoxide dismutase 1 (SOD1)
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what does each subunit of SOD1 bind to?
1 copper atom, 1 zinc atom
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mutations in this gene causes familial ALS
SOD1
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type of aggregation that occurs in ALS
aggregation of well-folded, structured proteins that clog other cytoplasmic components
SOD1 mutations promote production of copper-deficient misfolded species
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PrPC
- -normal prion protein
- -rich in -helices
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PrPSC
- - conformationally changed prion protein
- - rich in -sheets
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what leads to prion disease
aggregation of PrPSC
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types of prion diseases
- - Creutzfeldt-Jakob Disease (CJD)
- - Bovine Spongiform Encephalopathy (BSE/mad cow)
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types of CJD
- 1) sporadic/spontaneouss
- 2) familial/inherited defect in prion protein gene (Chr 20)
- 3) acquired through contaminated meat
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cause of cataracts
defective crystallin in the lens prevents the protein from acting as a chaperone, resulting in protein aggregates
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significant components of mature-onset cataracts
D-crystallin and S-crystallin
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signs of cataracts
- - inability to identify blues, purples, and greens
- - blurred vision
- - poor night vision
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