Artem Evdokimov AEVDOKIMOZ at
Fri Nov 29 02:58:59 EST 2002

Dear Aida,

It is not easy to predict whether something can be crystallized or not. It
is almost always possible to have the crystals provided that enough effort
has been spent - it is up to the researcher to determine just how far one is
willing to go to obtain crystals.
85 kDa 2-domain protein sounds reasonably tough but not impossible. You do
not mention what expression system, if any, you have available for this
target - it may be necessary to express this protein in various forms and
hosts, in order to obtain particular crystallization-friendly species. There
are numerous options for this, and even more options if you consider
truncations, individual domain crystallization, etc. It is just not feasible
to list all of this in a short email.

Regarding domains - you will most likely have to re-clone the domains if you
decide to go this route. Proteases aren't usually all that specific, unless
you (or Nature) have designed a very specific site (such as specific 3C
protease site e.g. TEV or related proteases). Your best bet is to contact an
experienced crystallographer and an experienced protein engineer, and ask
specific questions starting from the very beginning. In the absence of any
good advice, your next best bet would be to research specific literature,
find something as close as you can to the situation that you have and apply
logic and common sense.

All in all, you need to ask more specific questions and provide more details
for a more meaningful answer.

Good luck,

"Aida Baharuddin" <aidabaha at> wrote in message
news:3DE6AE78.F903157A at
Dear x-tal readers,
1. I would like to know, is it difficult to crystallize a protein
with a size of 85 kDa and it is predicted to have 2 different domain?
it is predicted to function as a transcription factor and also involved in
lipid metabolism.
2. Is it possible to clone and express a certain domain of the interest
if yes, how? I always heard that if the protein could not  be crystallized,
try to crystallize the N terminal or C terminal domain only. But i
don't know how to do it,  is it i have to digest or clone the domain

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