test 2: protein folding Flashcards
proteins become denatured by what
heating
protein denaturing causes the protein to what
unfold
what is a proteasome
causes misfolded proteins to get refolded or proteolyzed immediately
refolded meaning that it has no function
if the protein folds incorrectly what can happen to the cell
the cell can be killed
what happens to a protein after the polyubiquitin chain is attached to it
it signals to the cell that the protein needs to be destroyed so it undergoes protein degradation to cut it up and then it is refolded again into something that works
what chaotropic agents denature protein
guanidium chloride and urea
what structure do chaotropic agents affect
interactions that stabilize 30 structure
what is christian anfinsen known for
the denaturation and renaturation of ribonuclease A
what was the denaturation and renaturation of ribonuclease A
RNase A is an enzyme that breaks down RNase
- treated RNase A with urea and mercaptoethanol ( both of these unfolded the protein)
- anfisen removed the urea and merca and the protein refolded
-Rnase A refoled into OG native structure and regained full enzymatic activity
- showed that the enzyme could refold back
what was the conclusion of the anfisen RNAse experiment
- showed that the primary amino acid sequences contains all the information needed to specify the correct 3D structure
1o structure (sequence) codes for
3o structure
all the info needed to make a 3d structure is where
in 1o structure
what is favorable in protein folding
- negative DG
- negative DH
- increase in S
what specific energetic factors are favored
- hydrophobic effect
- formation of stabilizing interactions
- entropy of water
what is the hydrophobic effect
- non polar side chains are buried in the interior of the protein as it folds minimizing the exposure to water
- increases the entropy of the water meaning that is a more negative G
what interactions are formed during protein folding
- hydrogen bonds: back bone and side chain
- ionic interactions: oppositely charged amino acid
- van de waals interactions: closely packed atoms in the folded state
- disulfide bonds
what is levinthals paradox
- asking why proteins dont take forever to fold given that there can be so many shapes
- proteins fold through limited and specific pathways
what happens during protein folding
- polypep collapses due to the hydrophobic effect
- 2o structure forms
3o structure begins to form - final native state forms
what state is the most stable
the native state
what shape does a protein fold in
a funnel
what is in vitro
- easy folding
- folding by dilution in buffer
what is in vivo
- difficult to fold bc the cellular environment is crowded
- co translational folding
- high potential for misfolding and precipitation
what are chaperone proteins
help proteins fold
when were chaperone proteins discovered
during heat shock that is why theyare called heat shock proteins
what energy does protein folding need
atp hydrolysis energy
how is protein precipitation prevented
by DNAj and DNAk coating the unfolded protein and preventing denaturation/ precipitation
what large chaperon protein helps fold proteins in prokaryotes, cytosol of eukaryotes
Hsp60
where is the chaperone protein Hsp60 located
GroEL/GroES complex in E.coli
what is important about the GroEL/GroEs folding mechanism
it requires ATP hydrolysis
what is the purpose of disulfide isomerase
facilitates formation of correct disulfie bridges
what does peptidyl proline isomerase do
catalyses cic-trans isomerisaton of peptide bonds involving proline
what happens if a protein doesn’t get refolded
it can accumulate as precipitate which can resul tin severe chronic degenerative diseases that affect the brain and CNS
what diseases are associated with precipitated proteins
Prion- transmissible spongiform encephalopathies TSE
what are different types of TSE
BSE, mad cow diseaes, CJD/ nvCJD. human BSE
what are amyloid related diseases that are from precipitated proteins
alzheimers, parkinsons
what conformation changes when the protein misfolds
alpha helix turns into b sheet conformation and forms a cross B helicial core filament structure
why is too much amyloid bad
it can form plaque in the brain and disrupt cell function and cause neuronal apoptosis which is brain cell death
what can cause misfolding
- caused by genetics
what is a prion
proteinaceous infectious particle
what happens in a prion
- infection is when there is a change of 2o structure and conformation in the pathogenic protein and it converts from alpha to beta
what is kuru and what disease do they have
- tribe in papa new guniea and they ate dead loved ones and PrPSC prions were transmitted
what is CWD
a neurological disease in deer, elk, ad moose
why was it important that stanley prusiner won the nobel peace prizec
1st case of infectious agent being aprotein
what is CTE
chronic traumatic encephalopathy a diseae that can lead to demntia memory loss and depression
what protein can cause cancer if misfolded
p53 protein because it is a tumor supressor so it stops them before they grow if it is not working then it can cause them to grow
