Protein-DNA complex crystallization

From: umar farook
Date: 21 November 2011 15:59

Dear All,

I have been trying to crystallize protein DNA complex, but all the time i end up with DNA crystals. Even i changed the length of DNA many times but still no complex, DNA only crystallizes! Does anybody has idea, why do DNA crystallize by itself ? My protein behaves very nicely, Dynamic Light Scattering always shows nice values implies homogenous but once i tried to ran acidic native page but it shows little bit aggregated. The protein is highly hydrophilic and soluble, and has only three cysteines, is it there any possibility of aggregation due to cysteine, when overexpressed in E.coli ? and one more thing i mixed protein and DNA together and ran agarose gel to see any gel shift, indeed there is a binding, but when i take the same thing to set drops, only DNA crystals. Kindly suggest me, what could be done.

Thanks & Regards,

Umar Farook.S

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From: Francis E Reyes


Curious, how did you assess that your crystals only have DNA?

F

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Francis E. Reyes M.Sc.
215 UCB
University of Colorado at Boulder

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From: sxn214@psu.edu




Sent from my Verizon Wireless Phoneany possibility of aggregation due to cysteine, when overexpressed in E.*
coli* ? and one more thing i mixed protein and DNA together and ran agarose

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From: Phoebe Rice

What is Kd?

Also, in reply to earlier posts: it is sadly common in crystallizing large protein-DNA complexes to go through a couple dozen different duplexes and several dismally-diffracting crystal forms before finding a good one.

 Phoebe