Two conserved regions of SecY proteins from six Gram + bacteria were exploited in a PCR-based strategy for isolating a secY homolog from Streptomyces lividans (Sl). The nucleotide sequence of part of a 3.8-kb fragment showed that the secY homolog is flanked, at the 5 end, by the gene encoding ribosomal protein L15 and, at the 3 end, by an adenylate kinase-encoding gene. The deduced gene product of secY would have 437 amino acids (aa) and an M r of 47 200. Sl SecY shows 89.5, 56.1, 42 and 40% identity to its homologs from Streptomyces scabies, Brevibacterium flavum, Bacillus subtilis and Escherichia coli, respectively. Promoter-probe analyses indicated that the secY gene probably contains its own promoter.