Prions – morphing agents of disease
Activity 5
Hypothesising why prions are resistant to heat and digestion
Prions are made of protein. If prions from cows are proved to infect humans, how is it that they are not digested and broken down into their individual amino acids within the gut? How could they be resistant to the high temperatures used in cooking?
Teachers notes
Prions seem to resist the action of proteases and heat treatment (at comparatively low temperatures) because of the way in which the protein chain is folded. The normal prion protein is folded into four alpha-helices whereas the infective form of the protein folds into beta-sheets.
Even if they are not broken down by cooking or digestion, ingested prions would still need to be able to move from the digestive tract to the spinal cord and brain where they are found in the greatest number.
Intact prions (not broken down into their constituent amino acids) seem to be able to pass across the gut wall by a form of pinocytosis or perhaps through lesions directly into the blood stream. One suggestion of how it gets to the brain is via the lymphatic system to the spleen and then via spleen nerves to the spinal cord and brain.
Page updated June 2006.