Tat dependent export of E. coli phytase AppA by using the PhoD-specific transport system of Bacillus subtilis.

It has been shown recently that the twin-arginine signal peptide of Bacillus subtilis phosphodiesterase PhoD (SPPhoD) can mediate Tat dependent transport of proteins via its specific Tat-transport components. In order to test the use of Tat dependent transport signals for heterologous product synthesis, Escherichia coli phytase AppA was expressed under control of PhoD-specific export signals in B. subtilis. Induction of Tat components TatAd/TatCd was mediated by using a functionally altered PhoR/PhoP signal transduction system which regulates the expression of these components. AppA was highly susceptible to host specific extracellular proteases. Expression of appA in B. subtilis wprA strain resulted in the stable production of AppA. A fusion protein consisting of SPPhoD and mature AppA remained unprocessed, while introduction of the AppA signal peptidase cleavage site resulted in efficient processing of the fusion protein. Copyright 2004 WILEY-VCH Verlag GmbH & Co.