Introduction to Prions (1)

Question 1

What is prion?

Answer 1

“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.”

Question 2

What would you call the disease-causing prions?

Answer 2

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.”

Question 3

What are the stages in protein synthesis?

Answer 3

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.

Question 4

What are the levels of protein synthesis?

Answer 4

Question 5

What does each codon code for?

Answer 5

AMINO ACID

Question 6

Does each codon seq correspond to 1 amino acid?

Answer 6

no, multiple codons can code for a single amino acid

Question 7

How are amino acids connected?

Answer 7

peptide bonds

Question 8

What forms the secondary protein structure?

Answer 8

beta sheets
alpha helices

Question 9

What treatments render prions non-infective? However, what is the issue with this?

Answer 9

by protein and lipid disrupting agents (phenol, ether, NaOH, hypochlorite).

agents are highly toxic and corrosive.

Couldn’t use on dental instruments

Question 10

Do prions self-replicate?

Answer 10

yes

Question 11

Do prions have DNA?

Answer 11

NO, they are proteins.

unique feature

no genetic transmission needed to replicate

Question 12

What does PrP stand for?

Answer 12

prion protein

Question 13

What does PrPc stand for?

Answer 13

cellular prion protein

Question 14

What does Prpsc stand for?

Answer 14

scrapie prion protein

Question 15

What is the normal form of Prp?

Answer 15

cellular

endogenous, properly-folded form (α – Helix).

Question 16

What secondary structure does a normal form of PrP have?

Answer 16

4 alpha-helix

Question 17

What is the disease-linked form of PrP?

Answer 17

scrapie

disease-linked, misfolded form (β – sheet).

Question 18

What secondary structure does
the disease-linked form of PrP have?

Answer 18

beta sheet

2 alpha helices convert to beta sheets

Question 19

What is the commonality of PrPc and PrPsc?

Answer 19

have identical primary structures (i.e. amino acid sequence).

Question 20

What does PrPsc have a strong tendency to do?

Answer 20

PrPsc has a strong tendency to self-aggregate and form fibrils.

Question 21

What are 3 ways which the PrPc converts to a PrPsc?

Answer 21

• spontaneous mutation
• conversion
• inoculation - through infected tissues.

Question 22

How does the abnormal prion protein/ beta sheet convert more normal prions to mutated form?

Answer 22

has a higher propensity to replicate

leading to accumulation of the abnormal prion protein