Figure 1.9: Western blotting: examples
a.
Western blot of brain homogenates from uninfected (lanes 1 and 2) and
prion-infected (lanes 3 and 4) hamsters. Samples in lanes 2 and 4 were
digested with a proteinase enzyme (proteinase K). Samples in lanes 1 and
3 were not treated. Under these conditions, PrPC in lanes 2
and 4 was completely degraded, whereas approximately 67 amino acids were
digested from the PrPSc molecule to generate the smaller protease-resistant
PrP molecule, PrP 27-30.
b. Bar diagram of Syrian hamster PrP, which consists of 254 amino acids to illustrate the origin of the protein fragments shown in Figure 1.9a. After processing of the termini of the polypeptide, both PrPC and PrPSc consist of 209 amino acids. After limited proteolysis, PrPSc is truncated to form PrP 27-30, which is composed of approximately 142 amino acids.
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