Can anybody help me with this? I'm trying to purify a protein that has DNA as substrate, but I cannot seem to purify away the exonuclease. So when I try to assay for my protein, the DNA substrate is just chew up very fast. However, the SDS gel showed the protein prep was very clean. I use a NiNTA and size exclusion for purification. Also tried anion or cation exchange, which doesn't get rid of the exo's completely. What can I do to get rid of these exo activity completely? Is there any exonuclease-minus strain that I can use for over expression of my protein?
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Removing Exonuclease From Protein Prep
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