From:	Stephen Guilliot s.guilliot@**********.edu
Subject:	Ahh the wonders of biotech!
Date:	Fri, 23 Jun 2000 02:28:12 -0500

From: Michael Schmidt <Michael.Schmidt@****.uni-hannover.de>
>Proteines with these properties will have to be long inline
>macro-molecules. Perhaps they are to big to be produces inside of
>e-coli bacteria cells.
>Another explanation could be, that for bacteria based biochemical
>production a from the main genome separated dna-ring only bacteria
>possess is used. This ring can only have a specific lenght. If the
>dna-mask for the macro-proteine is too long for this ring the cell is not
>able to synthsize it.

Michael,
Your point is well taken. However, as I recall, spider silk macromolecules
are composed of smaller subunit proteins which covalently bond (strongly)
together. The bonding occurs outside the cell (triggered by pH?), since if
it happens inside, it becomes impossible to export. So, I believe that the
size of the protein alone will not prevent its use in bacteria. Thanks for
the reply.


From: "Sebastian Wiers" <m0ng005e@*****.com>
> Also just guessing here, a single celled creatures physiology may be
>disrupted by the production of complex proteins, while milk glands are
>supported by the animals body and can devote all thier energy to producing
>various protiens and such- adding a new one doesn't strain the physiology.
>It may just be the only way to do it, for bilogical reasons.
> Another problem (maybe the biggest) is that e-coli and yeast go thorugh
>many generations in the life of one goat or horse- mutation is almost
>inevitable, and it is very hard to separate the mutants from a culture.

Seb,
You correctly pointed out the problem of mutation, but there are ways to
prevent the loss of a target gene. Just remake the bioculture from frozen
stock after each harvest. The production of excess protein is disruptive to
the cell, as you pointed out. But that's OK, since usually the cells are
killed to harvest the product, anyway.
Also, single celled organisms are used to make most drugs because they are
so cheap. After all, you can grow bacteria/yeast by vat full, they're cheap
to feed, and don't have to be put out to graze. Even mice are avoided when
possible because they grow slowly (in comparison), require lots of hands on
maintenance, and don't produce the shear volume of protein that yeast can.
The only time animals are used for production is to provide some necessary
element that can't be found in a cheaper medium. In this case, that is the
mystery. Thanks for the input. It's cool to hear someone point out the
inevitability of evolution. :)

Steve G.