Introduction to Prions (1) Flashcards
What is prion?
“Protein of unknown function that resides on the surface of brain
cells”.
“An abnormal form of prion protein that in mammals includes
pathogenic forms that arise spontaneously (e.g. genetic mutation) or
transmitted (e.g. via infected tissue) and upon accumulation in the
brain cause a prion disease e.g. BSE or CJD.”
What would you call the disease-causing prions?
abnormal form of prion protein in the brain, pathogenic forms.
“An abnormal form of prion protein that in mammals includes
pathogenic forms that arise spontaneously (e.g. genetic mutation) or
transmitted (e.g. via infected tissue) and upon accumulation in the
brain cause a prion disease e.g. BSE or CJD.”
What are the stages in protein synthesis?
DNA, translated to a primary primary mRNA seq, then alternative splicing, the mature mRNA seq has been made.
exit the nucleus and codons recognised by tRNA and and translated in the ribosome.
polypeptide chain of amino acids.
What are the levels of protein synthesis?
What does each codon code for?
AMINO ACID
Does each codon seq correspond to 1 amino acid?
no, multiple codons can code for a single amino acid
How are amino acids connected?
peptide bonds
What forms the secondary protein structure?
beta sheets
alpha helices
What treatments render prions non-infective? However, what is the issue with this?
by protein and lipid disrupting agents (phenol, ether, NaOH, hypochlorite).
agents are highly toxic and corrosive.
Couldn’t use on dental instruments
Do prions self-replicate?
yes
Do prions have DNA?
NO, they are proteins.
unique feature
no genetic transmission needed to replicate
What does PrP stand for?
prion protein
What does PrPc stand for?
cellular prion protein
What does Prpsc stand for?
scrapie prion protein
What is the normal form of Prp?
cellular
endogenous, properly-folded form (α – Helix).
What secondary structure does a normal form of PrP have?
4 alpha-helix
What is the disease-linked form of PrP?
scrapie
disease-linked, misfolded form (β – sheet).
What secondary structure does
the disease-linked form of PrP have?
beta sheet
2 alpha helices convert to beta sheets
What is the commonality of PrPc and PrPsc?
have identical primary structures (i.e. amino acid sequence).
What does PrPsc have a strong tendency to do?
PrPsc has a strong tendency to self-aggregate and form fibrils.
What are 3 ways which the PrPc converts to a PrPsc?
- spontaneous mutation
- conversion
- inoculation - through infected tissues.
How does the abnormal prion protein/ beta sheet convert more normal prions to mutated form?
has a higher propensity to replicate
leading to accumulation of the abnormal prion protein
