1-47 Correcting Protein Defects

Question 1

the protein only hypothesis

Answer 1

it explains prion diseases (amyloid diseases)

Question 2

describe the protein only hypotehsis

Answer 2

Prion proteins (PrP) interchange between

PrPc - nonpathogenic, soluble, protease sensitive,mainly alpha helix

PrPsc - pathogenic, insoluble, protease insensitive, and 50/50 alpha helix beta sheet.

when PrPsc proteins come together, they bind together via beta sheet interactions that are very stable. this prevents them from chaging back into the PrPc form and also creates a nucleus which other PrPsc proteins rapidly bind

Question 3

pore hypothesis

Answer 3

supported by Islet amyloid polypeptide IAPP

posits that still developing soluble oligomers are more toxic than the mature fibrils in amyloid disease

as oligomers are growing, they diffuse into the cell membrane and form a pore to disrupt it

once a large enough beta confirmation fibril is formed, will bud off back into cytosol

Question 4

according to pore hypothesis, what happens when we introduce mature fibrils into affected cells?

Answer 4

could be protective - the IAPP proteins would aggregate with the fibrils (the template) in the cytosol instead of disrupting the cell membrane

Question 5

receptor hypothesis

Answer 5

supported by ab42

suggests that prion oligomers bind receptors and alters signal pathways

specifically, binding glutamate receptor in alzheimers and creutzfeldt disease.

studies preventing abeta42 and PrPc from binding the glutamate receptor in mice has been promising

Question 6

how does a defect or mutation affects properties of the protein and how this gives rise to disease symptoms

Answer 6

in prion diseases - beleived that normal PrP’s experience mutation that causes equilibrium to shift toward the PrPsc more than normal

this increases the likeliehood of a beta structure nucleation event

Question 7

what effect does the apolipoprotein E taking on the isoform ApoE4 have?

Answer 7

salt bridge formation between arg and glu residue causes preferential binding to VLDL and a-beta.

people with this isoform have greater risk of cardiovascular disase (due to VLDL bidning) and alzhiemers disease (a-beta binding)

Question 8

describe transthyretin amyloidosis

Answer 8

TTR protein that binds/transports thyroxine is mutated into form that can form amyloid fibrils

TTR is in equilibrium between two states - a tetramer and monomer

monomer forms amyloid

mutations that push equilibrium towards the monomer form cause the disease which spreads around the body causing mutliple organ failure

Question 9

amyloid cascade hypothesis vs other hypotheses that describe how “toxic folds” kill cells and cause disease

Answer 9

amyloid cascade - it is the mature fibrils that lead to cell death in amyloid diseases

other hypotheses maintain taht the formation of amyloids is a side effect of teh disease, and that soluble oligomers are what cause symtpoms

Question 10

what would be a viable strategy of lowering alzheimers risk?

Answer 10

disruption of the inter-residual salt bridges of ApoE4

Question 11

what would be a viable strategy to combat TTR amyloidosis

Answer 11

small drugs have been designed to bind TTR’s thyroxine binding site and stabalize the tetrameric form.

goal is to stabalize enough tetramer while still leaving thyroxine binding sites open

Question 12

Alpha-1-antitrypsin is a good example because..

Answer 12

its a serine protease and is an example of a disease due to misfolding that can result from either aggregation or lack of function

Question 13

describe the RCL loop and neutrophil elastase

Answer 13

NE sees the reactive center loop, bites it, forms covalent bond

loop cleaved and now is intserted into central beta sheet (has complemetnary sequences)

-it drags neutrophil elastase down to lower section of alpha 1

the interaction of alpha 1at and neutrophil elastase causes it to unfold (destabalizes it), which allows other proteases to come and degrade it

Question 14

two things that can go wrong with alpha-1-antitrypsin

Answer 14

1. when RCL inserts into beta sheet, it is sprung by itself. more stable, can’t go back and can’t inhibit anymore. If this happens enough due to mutation, can no longer inhibit neutrophil elastace which proceeds to chew up things it shouldnt
2. if insertion occurs without cleavage, and it mis-inserts into a neighbor molecule causing a stabalizing aggregating chain reaction. Can occur in liver where concentration is high. Builds up and causes liver failure

Question 15

the isomutation of alpha-1-antitrypsin causes..

Answer 15

destabaliziation of the beta sheet

Question 16

congo red staining is for

Answer 16

amyloid/myeloid

Question 17

what amino acids suggest an alpha helix?

Answer 17

the helix forming alanine, arginine, and leucine. mainly alanine

Question 18

will give array of amino acids and ask if it will stabalize or destabalize the alpha helix

Answer 18

-if it interrupts the i+4 and i salt bridge, it will destabilize

Question 19

what pattern do beta sheet amino acids follow?

Answer 19

polar-non polar- polar - non polar

charged-uncharged-charged- uncharged

Question 20

coil-coil is suggested by

Answer 20

heptad repeats - structural motif that consists of a repeating pattern of seven amino acids: a b c d e f g H P P H C P C. where H represents hydrophobic residues, C represents, typically, charged residues, and P represents polar (and, therefore, hydrophilic) residues.