as Host for Expression of Multisubunit Membrane Protein Complexes.

is a convenient host for the expression of proteins, but the heterologous production of large membrane protein complexes often is hampered by the lack of specific accessory genes required for membrane insertion or cofactor assembly. In this study we introduce the non-pathogenic and fast-growing as a suitable expression host for membrane-bound proteins from . We achieved production of the primary Na pump, the NADH:quinone oxidoreductase (NQR), from in an active state, as indicated by increased overall NADH:quinone oxidoreduction activity of membranes from the transformed , and the sensitivity toward Ag, a specific inhibitor of the NQR. Complete assembly of NQR expressed in was demonstrated by BN PAGE followed by activity staining. The secondary transport system Mrp from , another membrane-bound multisubunit complex, was also produced in in a functional state, as demonstrated by Li transport. is a promising expression host for the production of membrane protein complexes from Gram-negative pathogens.