DISTRIBUTION IN THE GENUS STREPTOMYCES OF A HOMOLOG TO NUSG, A GENE ENCODING A TRANSCRIPTIONAL ANTITERMINATOR

The presence of the vbrA gene encoding the transcriptional antiterminator NusG equivalent protein of Streptomyces virginiae was tested for in 73 Streptomyces species by Southern hybridization. Fifty-five strains (75%) including S. griseus, S. lividans TK-21 and S. coelicolor A3(2) showed clear hybridization signals, indicating wide distribution of vbrA or vbrA homologs in Streptomyces species. With hybridization patterns against 3 different probes, i.e., probes covering vbrA alone, the downstream gene rplK alone, and both vbrA-rplK, the 55 strains were classified into 4 groups. In the groups I, II and III (total 50 strains) vbrA was found to be adjacent to rplK, indicating that the gene arrangement vbrA-rplK is common in Streptomyces and that these genes may constitute a part of gene cluster encoding several components of the transcription and translation apparatus, as in Escherichia coli.