DegU

DegU is a response regulator protein in Bacillus subtilis that functions as part of the DegS-DegU two-component signaling system. It mediates transcriptional responses to environmental and population signals by being phosphorylated by the sensor kinase DegS. In its phosphorylated form, DegU-P acts as a DNA-binding transcription factor; the level of phosphorylation modulates distinct cellular programs. Non-phosphorylated DegU also participates in regulatory circuits, often antagonizing or fine-tuning DegU-P–dependent responses.

DegS-DegU coordinates a broad set of traits, including exoprotease production, motility, biofilm formation, and competence for DNA uptake. Depending on the level of DegU-P and the cellular context, DegU can activate or repress target genes, and work in concert with other regulators. DegU-P influences the expression of extracellular proteases and surface-associated enzymes, while facilitating or repressing competence development during the stationary phase. The regulator SwrA interacts with DegU-P to control swarming motility and certain protease genes in some strains.

DegU activity is modulated by signals that feed into DegS, and phosphatases provide a means to reverse the signal, allowing dynamic response to changing conditions. The DegS-DegU system is a paradigm for how two-component signaling can govern complex differentiation programs in Bacillus species. Its study informs understanding of bacterial development, multicellular behavior, and industrially relevant protease production.