MAJOR PROBLEM IN EXPRESSING GST TAGGED PROTEIN - (Jan/18/2008 )

I am expressing an Mtb protein from the pGEX6P1 vector.
However despite multiple attempts I am able to express ONLY the tag and not the fusion protein. I am doubly sure that the gene is in frame with the vector promotor and tag and there is no stop codon interfering.
Has anyone faced any such problem?
Please help me.

Hi,

I have a similar problem in that my GST-fusion protein dissociates to give the tag and the protein of interest after a few days storage at 4 degrees. We think that this is because my protein is highly negatively charged and so tends towards aggregation which makes the fusion unstable (although we're not sure!!). Does your protein have any characteristics that would make it unstable (charges, protease activity)??

P