Expression of a new operon from Bacillus subtilis, ykzB-ykoL, under the control of the TnrA and PhoP-phoR global regulators.

The ykzB and ykoL genes encode two peptides, of 51 and 60 amino acids, the functions of which are unknown. The ykzB and tnrA genes are contiguous and transcribed divergently. Expression of ykzB and ykoL is induced by glutamate and is under the control of the TnrA global regulator of nitrogen utilization. TnrA regulated its own synthesis in glutamate minimal medium. Two DNA sequences (TnrAB1 and TnrAB2) homologous to the TnrA binding site are present in the region between tnrA and ykzB. Deletion mapping indicated that the TnrAB2 binding site was involved in activation of the ykzB promoter. In addition, transcription of tnrA depends on the presence of the TnrAB1 binding site. The ykzB and ykoL genes are probably in the same transcriptional unit. A single promoter involved in transcription in the presence of glutamate was mapped by primer extension. ykoL expression was induced by phosphate limitation and depended on the PhoP-PhoR two-component regulatory system. Its promoter was mapped to the region between ykoL and ykzB. Four boxes similar to the PhoP binding site are present upstream from the ykoL promoter. These boxes are probably recognized by PhoP approximately P during the activation of transcription in phosphate limitation conditions.