Nucleotide sequence of genes hrdA, hrdC, and hrdD from Streptomyces coelicolor A3(2) having similarity to rpoD genes.

The complete nucleotide sequences were determined of hrdA, hrdC, and hrdD from Streptomyces coelicolor A3(2). They indicate the presence of a single open reading frame in each gene coding for polypeptides of 396 (43,747 daltons), 339 (38,173 daltons), and 332 amino acid residues (37,190 daltons), respectively. These amino acid sequences revealed extensive similarities with the principal sigma factors of Bacillus subtilis, Escherichia coli, Mxyococcus xanthus, Pseudomonas aeruginosa, and also the katF gene product of E. coli. Besides the highly conserved amino acid residues in the "rpoD box" region, alignment of hrd gene products and the known principal sigma factors and sigma-related factors allowed us to postulate a common basic structure for the principal sigma type factors as distinct from the alternative sigma factors.