Dear Jerry,
One way I can think of would be to try the magical polymer NV-10 sold by
Novexin (UK). It does actually work very well for proteins with low
solubility. You'd add a few mg/ml of polymer to each protein solution, mix
the two and see what happens. This polymer has already saved several of my
poorly soluble proteins and I hear from others that it worked well for them,
too.
If you're desperate - I would recommend rational surface mutagenesis. We,
and others, have designed surface mutants with greatly improved solubility
:-) Or fuse with something nice and soluble.
Artem
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From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Jerry
McCully
Sent: Wednesday, December 12, 2007 3:31 PM
To: [log in to unmask]
Subject: [ccp4bb] protein precipitated when they formed a complex
Dear All,
Recently I posted a question about protein induced protein
precipitation.
Firstly I'd like to thank many folks for their good ideas.
Later on I did a titration experiment with one protein concentration
fixed at 0.4mg/ml(about 10uM). Now it is clear that these two proteins
stoichiometrically precipitated when they formed a 1:1 complex. The excess
of individual proteins was just soluble in the buffer.
How come these two proteins co-precipitated when they formed a complex?
Does anyone know some methods to keep the complex soluble enough for
crystallization?
By the way, there is some additional information about the individual
components. One has a pI of 6.5, and the other has a pI of 10.
Any suggestions will be highly appreciated.
Jerry McCully
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