MULTIPLE SIGMA-FACTOR GENES IN BREVIBACTERIUM-LACTOFERMENTUM - CHARACTERIZATION OF SIGA AND SIGB

Four rpoD hybridizing signals have been identified in the chromosome o f Brevibacterium lactofermentum. Two rpoD-like genes, sigA and sigB, h ave been cloned and sequenced, and they encode principal sigma factors of the RNA polymerase. The deduced amino acid sequences of SigA and S igB showed very high similarities to those of Mycobacterium smegmatis MysA and MysB proteins, respectively, and also to those of HrdB protei ns from different Streptomyces species. SigA and SigB maintain the con served motifs of sigma(70)-like principal sigma factors. sigB is close ly linked to the dtxR gene (encoding a repressor of iron-regulated pro moters homologous to the diphtheria toxin repressor from Corynebacteri um diphtheriae).