I've expressed a GST-fusion protein (original size ~24 kDa). The protein is expressed and shows on SDS-PAGE a band of correct size. However my purification of the protein (using Glutathione-Agarose beads, Sigma according to manufacturer) is not working. I've tried things like, changing buffers, pH, incubation time etc. The control (GST only) works ok, and also another fusion protein has no problems. The protein fused to GST is highly negatively charged at the pH at which the experiments are done. Does somebody have any suggestions?
Thank you,
S.R.M. Martherus
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