Genetic and molecular analysis of the rpoD gene from Lactococcus lactis

A gene of Lactococcus lactis ATCC19435, the product of which is homologous with the principal sigma factors of Escherichia coli and Bacillus subtilis, was cloned and sequenced. The deduced amino acid sequence of the 340-residue protein and the upstream open reading frame of the cloned gene showed a homology to B. subtilis sigma 43 factor (the rpoD product) and DNA primase (the dnaE product), respectively, suggesting that L. lactis also has the rpoD operon. Surprisingly, introduction of the cloned L. lactis rpoD gene into a rpoD temperature-sensitive mutant of E. coli caused partial complementation.