Cloning and expression in Escherichia coli of genes encoding a multiprotein complex involved in secretion of proteins...

The genes encoding the multiprotein membrane-bound ribosomal protein (MBRP) complex (mrp genes), associated with membrane-bound ribosomes in Staphylococcus aureus, were cloned in Escherichia coli. All four components (molecular sizes 71, 60, 46, and 41 kilodaltons) of the MBRP complex were expressed from an 8.5-kilobase DNA fragment as judged by Western blot (immunoblot) analysis. The order of the individual genes within the cloned DNA fragment was determined by deletion mutagenesis and subcloning of various restriction fragments. Three RNAs, transcribed from the same DNA strand, were identified within the MBRP-coding region: one large RNA of approximately 5.9 kilobases, presumably coding for all four MBRP components, and two minor RNAs, coding for MBRP-71 and MBRP-60. The two minor RNAs seemed to be transcribed from promoters within the large transcription unit. Attempts to make insertional inactivations of the mrp genes with an internal 600-base-pair DNA fragment of the MBRP-coding region as a target were unsuccessful, presumably because such insertions are lethal.