Twin-arginine translocation pathway in Streptomyces lividans

The recently discovered bacterial twin-arginine translocation (Tat) pathway was investigated in Streptomyces lividans, a gram-positive organism with a high secretion capacity. The presence of one tatC and two hcf106 homologs in the S. lividans genome together with the several precursor proteins with a twin-arginine motif in their signal peptide suggested the presence of th e twin-arginine translocation pathway in the S. lividans secretome. To demo nstrate its functionality, a tatC deletion mutant was constructed. This mut ation impaired the translocation of the Streptomyces antibioticus tyrosinas e, a protein that forms a complex with its transactivator protein before ex port. Also the chimeric construct pre-TorA-23K, known to be exclusively sec reted via the Tat pathway in Escherichia coli, could be translocated in wil d type S. lividans but not in the tatC mutant. In contrast, the secretion o f the Sec-dependent S. lividans subtilisin inhibitor was not affected. This study therefore demonstrates that also in general in Streptomyces spp. the Tat pathway is functional. Moreover, this Tat pathway can translocate fold ed proteins, and the E. coli TorA signal peptide can direct Tat-dependent t ransport in S. lividans.