The NAD synthetase NadE (OutB) of Bacillus subtilis is a sigma(B)-dependent general stress protein

The identification of sigma(B)-dependent general stress proteins is a useful strategy to understand the physiological role of the unspecific stress response in Bacillus subtilis. By N-terminal sequencing of B. subtilis stress proteins Gsp38 was identified as the NAD-synthetase (NadE). NadE was previously characterized as spore outgrowth factor B (OutB) conferring a temperature-sensitive spore outgrowth defective phenotype. Transcriptional studies showed that nadE is strongly induced in response to heat, ethanol and salt stress or after starvation for glucose in a sigma(B)-dependent manner. Two promoters are involved in transcriptional initiation, the sigma(A)-dependent upstream promoter contributes to the basal level during growth, whereas the sigma(B)-dependent downstream promoter is induced after different stress conditions.