Protein folding in health and disease\ Flashcards
ATP synthase
Made of protein, molecular motor found in mitochondria, responsible for making ATP by rotating a turbine - there are two motors
3 stages of making DNA that must be error free
- DNA needs to be without mutations that change meaning of its code
- RNA needs to be transcribed properly without error
- Protein needs to be translated, folded and located in the correct part of cell
What is the central dogma?
DNA - RNA - protein
What is transcription?
DNA to mRNA (RNA polymerase)
What is translation?
In cytosol, mRNA - polypeptide
What is protein synthesis?
Ribosome reads mRNA and assembles chain of amino acids, joined by peptide bonds
tRNA binds each triplet of RNA bases, leaving behind amino acid
How does the secondary structure of a protein form?
Hydrogen bonding between oxygen and nitrogen backbone
Strong pull on electrons, giving them negative charges
Hydrogen atoms have +ve charges
Oppositely charged atoms attracted to each other along chain
How does tertiary structure of a protein form?
Irregular folding due to interactions between R groups of amino acids
Forms ionic bonds
Polar forces - hydrophilic R groups bond with one another or turn outwards and bond with water
Where do covalent bonds form in amino acids?
Between sulphur atoms in R groups
How many amino acid chains form G-proteins?
3
Membrane proteins
Enzymes, receptors, anchors and transports (CFTR)
What is CFTR?
Chloride transporter
Where is translocon?
ER
makes membrane proteins
How many amino acid and alpha helices in CFTR?
1480 amino acids
12 alpha helices
Where is translocon?
Underneath ribosome
What does translocation do?
Ribosome sits on top and inserts polypeptide so it is integrated into membrane
Protein pore through which proteins are synthesised
How are proteins transported to cell membrane?
Golgi
What happens when membrane proteins enter at ER?
SRP binds to signal sequence of polypeptide when it comes from ribosome
Pauses protein synthesis until complex with SRP, ribosome and amino acid chain find SRT receptor on ER
When this happens, new peptide chain is inserted into translocon channel, where it enters ER
Protein synthesis occurs when SRP released from ribosome
CFTR synthesis?
Transcription - translation and protein folding - post-translational modification - protein trafficking - surface expression
Wuality control when making CFTR
- Cells have quality control mechanism to deal with misfolded/aggregated proteins
- CFTR happens in ER
- If protein is salvageable then it is refolded in ER
- If protein is terminally refolded, passes back into ER where it is degraded by protease enzymes
What is the p.Phe508del mutation?
Deletion of 3 DNA bases which result in missing F F
Phenylamine amino acid at position 508
Protein can’t fold correctly
What happens to misfiled CFTR?
Held in ER and degraded
When will CF occur?
p.Phe508del can’t perform function because it doesn’t reach plasma membrane of cell
How does p.Phe508del reach membrane?
Travels from ER through ERGIC through Golgi to plasma membrane
Treatment for CF
Bronchodilators, antibiotics, corticosteroids, pulmozyme, insulin, biphosphonates, vaccines/flu jabs
Reduction in protein function
Class 3 and 4 mutations
Reduction in amount
class 1,2,5,6 mutations = correctors
What do Potentiators do?
Increases activity of defective CFTR at cell surface
Can act on conductive or gating defects
What is a gating defect?
CFTR channel doesn’t open and allow CL- through
What is a conductance defect ?
Reduced flow of ions
What is a potentiatior?
Binds to channel which enhances opening so allows Cl- through in both mutations
What is a corrector?
Overcomes defective protein processing that results in production of misfiled CFTR - increase movement of CFTR to membrane
p.Phe508del mutation - protein is detected as misfiled and degraded
Corrector stops protein being degraded
What are production correctors?
Instruct ribosomes to read through premature termination codons during matrix translation
What is VX-770?
Ivacaftor and KALYDECO
Is VX-770 a potentiator or corrector?
Potentiator
What does VX-770 do?
Binds to CFTR and increases opening of channel and restores Cl- transport
Helps channel open and close to move Cl-
What class of mutation is p.Phe508del?
2
What is lumicaftor?
VX-809
it is a corrector that targets p.Phe508del CFTR to increase number of proteins trafficked to cell surface
What is orkambi?
Lumikaftor and ivacaftor
What does orkambi do?
Gets CFTR to cell surface and facilitates channel opening and closing
Why is orkambi good?
Slows decline in lung function
Increased BMI and FEV1
Who can have orkambi?
People with CF who are older than 2 with two copies of F508
Alzheimer’s disease
AChE inhibitors prevent AChE from braking down ACh, this leads to increased concentration of ACh between nerve cells
- Alzheimer’s - amyloid plaques and neurofibrillary tangles
- Alzheimer’s can be treated with AChE inhibitors = increased ACh = increased communication between nerves which can alleviate/stabilise symptoms
- Amyloid plaques: amyloid-beta peptides, proteolytic processing of APP protein, BACE1 and gamma secretase enzymes
- Alzheimer’s therapeutic targets: inhibiting BACE1 and secretase
