Insolubility of double-tagged protein

[Ditlev Brodersen]

Hi,

  we are having some trouble with a doubly-tagged (His in the N-terminus,
GST in the C-terminus) expressed in E. coli 834(DE3) pLysS which seems to
have very low solubility in our lysis buffer.

  I know this is a standard question, but what are the best things I can do
in order to optimise the amount of soluble protein?

Thanks in advance,

  Ditlev