Subcellular localization of signal peptide fusion proteins expressed in E. coli

For expression of some proteins in Escherichia coli, export to the periplasmic space is preferred over conventional expression in the cytosol. Export can be accomplished by fusing the coding sequence to DNA encoding a signal peptide (e.g., using pET-22b), which is cleaved by the bacterial signal peptidase as the protein is exported into the space between the inner and outer membranes of E. coli. This protocol uses osmotic shock to release polypeptides from the periplasm. Although not quantitative, it should provide preliminary information on the cellular location of signal peptide fusion proteins.