Cloning and sequencing of the secY homolog from Coryneform bacteria

A conserved domain of the secY genes from Bacillus subtilis, Mycoplasma capricolum and Escherichia coli was used to design degenerate oligodeoxyribonucleotides. These synthetic DNA sequences were used to screen a lambda library of Brevibacterium flavum MJ233. A 1.5-kb KpnI fragment of a recombinant lambda phage containing the secY homology from Br. flavum MJ233 was subsequently subcloned into plasmid pUC118. The complete nucleotide (nt) sequence of the cloned fragment indicated that the deduced gene product of the Br. flavum secY homolog is composed of 440 amino acids (aa) with a deduced M(r) of 47,871. Comparison of this aa sequence to the corresponding sequences from E. coli and B. subtilis revealed a high degree of conservation, and suggested that the Br. flavum secY homolog is a membrane protein containing ten transmembrane segments. In addition, we could identify, downstream from secY, a putative coding sequence of the enzyme adenylate kinase. This gene organization is identical to that observed in the B. subtilis genome.