[Biosynthetic regulation of extracellular ribonucleases in native strains of bacilli and in recombinant strains of Escherichia coli]

Abstract

Regulation of the biosynthesis of extracellular ribonucleases of Bacillus amyloliquefaciens H2 (barnase), Bacillus intermedius 7P (binase), and Bacillus pumilus KMM 62 (RNase Bp) was studied in their native strains and recombinant Escherichia coli strains. Recombinant plasmids were obtained that contained genes encoding barnase, binase, and RNase Bp under the control of their own regulatory sequences (plasmids pMT415, pML5, and pML61), genes encoding barnase and binase under the control of the tac promoter and the phoA leader sequence (plasmids pMT416 and pML163), and the binase-encoding gene under the control of the regulatory sequences of the barnase and RNase Bp genes (plasmids pML53 and pML67, respectively). Inorganic phosphate (Pi) inhibited the biosynthesis of binase and RNase Bp in natural strains B. intermedius 7P and B. pumilus KMM 62 and recombinant E. coli strains when genes encoding these RNases were under the control of their own regulatory sequences. In contrast the biosynthesis of barnase-either in the natural B. amylolique-faciens strain or in recombinant E. coli strains-was not affected by Pi. Neither did inorganic phosphate produce any effect on the biosynthesis of binase when the binase-encoding gene was under the control of the barnase gene promoter (pML53). The leader sequences and promoters were found to be similar in the binase and RNase Bp genes and differed considerably from the leader sequence and promoter of the barnase gene. The promoter regions of the binase and RNase Bp genes, but not of the barnase gene, contained sequences that resembled the Pho box of the phosphate regulon from E. coli.