Protein export in bacillus subtilis and escherichia coli

The export of heterologous proteins in Bacillus subtilis and Escherichia coli is often inefficient. Frequently observed problems are: 1) accumulation of the precursor form of the exported protein in the cytoplasm or in the membrane; 2), inefficient or incorrect processing of the precursor; 3), inefficient release of the processed protein from the cell-envelope; and 4), proteolytic degradation of the exported protein. Several distinct steps in the export of proteins, involving properties of both the exported protein and the cellular protein export apparatus, can be conceived to account for these problems. The main purpose of the investigations described in this Thesis was to determine whether the processing of precursors of, in particular heterologous, exported proteins by signal peptidase I (SPasc I) might be a rate-limiting step in protein export. ... Zie: Summary and general discussion