Functioning of the stable signal peptide of the pCloDF13-encoded bacteriocin release protein.

The pCloDF13-encoded bacteriocin release protein (BRP) is a lipoprotein which is synthesized as a precursor with an amino-terminal signal peptide that appears to be stable after cleavage. The role of the stable signal peptide in the functioning of the BRP was studied with respect to the release of cloacin DF13, 'lysis' and leakage of periplasmic proteins. The BRP gene fragment encoding the stable signal peptide was replaced by a fragment encoding the unstable peptide of the murein lipoprotein (Lpp). The resulting hybrid protein was normally acylated and processed by signal peptidase II, leaving no stable signal peptide in the cells. Expression of the hybrid protein did not result in the specific release of cloacin DF13, whereas 'lysis' and the release of periplasmic enzymes were unaffected. These results indicated a role for the stable BRP signal peptide in the translocation of cloacin DF13 across the cytoplasmic membrane.