A novel member of the subtilisin-like protease family from Bacillus subtilis.

aprX is a 1326 bp gene of Bacillus subtilis strain 168 that encodes a serine protease, probably intracellular, characterized by significant similarity with subtilisins, thermitases and pyrolysins. Transcription analysis, performed by RT-PCR and primer extension, allowed the localization of the active promoter and showed that aprX is expressed in stationary phase. The pattern of expression of aprX and its dependence on various transition state regulatory genes (degU, degQ, hpr, abrB, sinR), monitored by lacZ transcriptional fusions, are distinctive from those of subtilisin and other degradative enzymes. aprX is not essential for either growth or sporulation.