- Daesil Nam: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, 440-746, Korea.
The PhoP response regulator and PhoQ.sensor, which are encoded by the phoPQ operon, constitute the PhoP/PhoQ.two-component system. Genome-wide transcription analysis revealed that heterologous expression of the RstB protein, a sensor of the RstA/RstB two-component system, leads to enhanced transcription of PhoP-activated genes in wild-type Salmonella. We determined that RstB-induction increases the levels of PhoP mRNA as well as PhoP protein, while lack of the phoPQ genes abolishes RstB-promoted transcription of the PhoP-regulated genes. This regulatory function of RstB did not require its enzymatic activities, and thus the truncated RstB protein containing only periplasmic and transmembrane regions was able to promote PhoP-activated transcription. The RstB protein appeared to target the PhoQ.sensor rather than the PhoP response regulator because RstB-induction failed to enhance transcription of the PhoP-regulated genes in a strain maintaining the normal PhoP function, even without PhoQ.