Difference - (Mar/11/2006 )

Can any body explain me difference between Periplasmic and Cytoplasmic Space on the basis of Protein Solubility.
Best regards

The main difference between periplasma (the space between plasma membrane and outer membrane in gram-neg. bacteria) and cytoplasma is that the periplasma has an oxidative milieu while the cytoplasma has not.
So the periplasma would "equal" (only in terms of pH; not functional, in bacteria it is used for processes that invove toxins and would damage the cell if they took place within the cell) the ER in eukaryotes.
Actually, there has been an (older) approach to produce antibodies in E.coli by adding a signal sequence for transport to the periplasm as the S-S bridges can form there. (there must be a paper by skerra & plückthun and whoever, approximately 1990 about that).
So my guess would be that such proteins would form (insoluble) inclusion bodies in the cytoplasm, and are soluble and functional in the periplasm.

hope that is some kind of helpful...