Remove DNA from protein prep

Michael Kawalek kawalekm at
Fri Mar 2 13:07:33 EST 2001

Dear Bernard

I method I've used for restriction enzyme purification uses concentrated
streptomycin to precipitate DNA.  I originally used this clarification step for
the purification of recombinant EcoRI overexpressed in E. coli

Here's a quick outline

1) rupture your cells by whatever method you are using .  I used a french press.

2) clear the lysate by centrifuging for 1hr+ at 100,000 g

3) add 0.2 vol of 25% filter sterile streptomycin disolved in your extraction
buffer.  Mix for 45-60 minutes at 4oC.

4) Pellet the streptomycin/DNA complexes at 45,000g for 10-15 minutes and save
the DNA free supernatant.

5) continue with whatever purification procedure you are using.

Hope that works for you!

>I want to use a crude protein prep to do
>a gel-shift assay but I seem to have DNA
>in the prep. Does anyone have a suggestion
>for removing the DNA? I thought about using
>DNAse, but then how do I get the DNAse

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