A nonessential signal peptidase II (Lsp) of Myxococcus xanthus might be involved in biosynthesis of the polyketide antibiotic TA

Myxococcus xanthus is a gram-negative soil bacterium that produces the poly ketide antibiotic TA. In this study, we describe the analysis of an M. xant hus gene which encodes a homologue of the prolipoprotein signal peptidase I I (SPase II; lsp). Overexpression of the M. xanthus SPase II in Escherichia coil confers high levels of globomycin resistance, confirming its function as an SPase II. The M. xanthus gene encoding the lsp homologue is nonessen tial for growth, as determined by specific gene disruption. It has been map ped to the antibiotic TA gene cluster, and the disrupted mutants do not pro duce the antibiotic, indicating a probable involvement in TA production. Th ese results suggest the existence of more than one SPase II protein in M. x anthus, where one is a system-specific SPase Il (for TA biosynthesis).