abaB, a putative regulator for secondary metabolism in Streptomyces.

A chromosomal DNA fragment from Streptomyces antibioticus ATCC11891 was isolated by its ability to stimulate actinorhodin and undecylprodigiosin biosynthesis in Streptomyces lividans TK21. This fragment includes two open reading frames, whose deduced translated products resemble enzymes involved in sulfur metabolism (ORF1) and LysR-type transcriptional regulators (ORF2). The cloning of the promoter region of ORF2 (abaB) in high copy number led to overproduction of both antibiotics suggesting that this phenotype might well be due to titration by this region of one or more proteins. Southern blot analysis revealed that abaB gene is highly conserved among all streptomycetes tested.