what is alive

Mario Vaneechoutte Mario.Vaneechoutte at rug.ac.be
Wed Sep 25 19:03:35 EST 1996

Martijn Huynen wrote:
> There is one fundamental difference between prions and viruses.
> The latter evolve and adapt, whereas the former (as far as I
> understand) do not.
> This would make viruses more alife than prions.
Randy Zauhar wrote:
>   But at the same prions must evolve in a sense   mutations
>  in the host protein might make the prion conformation unstable, thus acting
>  as a lethal mutation for the prion. At the same time, another mutation might
>  compensate for the first change, and restore the possibility of adopting the
>  prion conformation. Thus the ability to carry the "information parasite"
>  is a product of the evolutionary process. Of course that is not the same
>  thing as the prion "itself" adapting, since information needs a carrier
>  if it is to undergo transformation.

There are prion fylogenetic trees (can't find the refernces). Some
sequence changes do occur. At which degree these are adaptive is unclear
to me.
This 'evolution' could have been expected: all information which is not
copied at 100% copy fidelity while 'evolve': some of the descendants
will not be identical to the parent.

(The only way out to stop such evolution is strong selection against
mutants, in cases where only the parent (wild type) information seems to
be 'viable'. I don't think this is ever the case.)  -- 

Mario Vaneechoutte
Laboratory Bacteriology & Virology
Blok A, De Pintelaan 185
University Hospital Ghent
Belgium 9000 Ghent
Tel: +32 9 240 36 92
Fax: +32 9 240 36 59
E-mail: Mario.Vaneechoutte at rug.ac.be

All opinions expressed here are my wife's, not mine.

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