Hi -

I do not think there are "rules". There is a logic, to never truncate within secondary structure elements, and to prefer to delete regions that have a high probability to be disordered.

With excuses for the non-ccp4 plugin, you can use our web server to help you design these.

http://xtal.nki.nl/ccd/Welcome.html


A.


On Mar 10, 2010, at 12:45, Claudia Scotti wrote:

 
Dear All,
 
I'd like to espress a protein for crystallisation as a whole, but also to try separate expression of its two domains.
 
Although prediciting domain boundaires is not difficult, I know that it is worthwhile testing several constructs to improve espression in soluble form. In several works I've seen that the choice is to keep or give up some aminoacids (for example 4 or 5) at the N and/or C-termini and to test them to see which expresses best.
 
I was wondering if there are defined  "rules" to choose these variants and/or to modify the N and C termini of a protein of interest when it is not important to keep them "true" (=native) in order to optimise expression levels.  
 
Is there any good reference about this, please?
 
Personal experiences are welcome.
 
Many thanks,
 
Claudia


Claudia Scotti Dipartimento di Medicina Sperimentale Sezione di Patologia Generale Universita' di Pavia Piazza Botta, 10 27100 Pavia Italia Tel. 0039 0382 986335/8/1 Facs 0039 0382 303673



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