The nusG genes of Streptomyces griseus and Streptomyces coelicolor A3(2) were cloned by the DNA-probing method with synthetic oligonucleotides designed on the basis of the nucleotide sequence of the nusG gene of Streptomyces virginiae. The amino acid sequences of the NusG proteins deduced from the nucleotide sequences showed significant homologies to those from a variety of microorganisms. Nucleotide sequence analysis of the region upstream of the nusG gene of S. griseus revealed the presence of the secE gene, suggesting that secE and nusG are organized as an operon as is found in other microorganisms.