Dear All,
Recently I was trying to crystallize a
complex of two proteins(40kD vs 20kD). TO my surprise, precipitates immediately
appeared in the solution even when I mixed these two proteins at about
1mg/ml. However, the individual proteins were just soluble and stable
in the same buffer. From the binding studies I knew that the affinity
between them was lower than 1uM therefore I could not purify the complex
by gel-filtration.
I checked the precipitates by SDS-gel. The majority of the precipitates were
the bigger protein. I'd like to mention that the smaller one was a protein with
the pI above 10.
Did the smaller protein induce the precipitation of the bigger one?
Does anybody know some tricks to avoid the
precipitation so that the protein complex could be concentrated enough
for the crystallization trials?
Many thanks in advance.
Jerry McCully
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