Prions, Normal and Pathogenic.
(A) Aug 15, 2004 Dov, in biologicalEvolution forum.
Re Scientific American July 2004, "Detecting Mad Cow Disease", SB Prusiner.
Genesis and replication modes of pathogenic prions curiously connote initial genesis and evolution of life, maybe from an RNA-related conformation. In both cases the process-enabling-moving circumstances are presence of the precursors of the Bingo Conformation plus a favorable energy balance.
Is it probable/possible, therefore, that the switch from normal to pathogenic prions is enabled and moved by a replacement of a component amino-acid such as tryptophane/niacin ?
(B) Aug 28, 2004 Dov, in biologicalEvolution forum.
The subject intrigues me because back in the early '50s I effected encephalomyelitis in fowls by inadequate levels of niacin or tryptophane and found that the minimal required level of these amino acids for the type of fowl was related to the physiology/weight/activity characteristics of the different fowl types.
My gut feeling (obviously not experimental evidence) is that PrPc to PrPSc conversion is indeed a "posttranslational conversion", initiated and maintained by a replacement of an amino acid, initiated and chain-reacting due to an energetically effected equation situation, on one side the PrPc precursors and on the other side the precipitating PrPSc.
Now I just read (The Scientist) updated reports that purified PrPSc do not replicate and that indeed various PrPSc's differ in amino acid component(s) .
Therefore it is required now to learn if tagged PrPc shows up in the PrPSc, or not, for finding if the PrPSc is formed from PrPc, or if it is formed instead of and to the exclusion of PrPc.
Also these data enhance the probability that the pathogenic PrPSc's include an adjunct "agent", lost upon PrPSc purification, that directs the preferred formation of PrPSc.