UhpA

UhpA is a response regulator protein that is part of the UhpA/UhpB two-component regulatory system found in Escherichia coli and related bacteria. It controls expression of the high-affinity glucose-6-phosphate transporter gene uhpT, enabling uptake of extracellular glucose-6-phosphate (G6P).

UhpA belongs to the OmpR/PhoB family of transcription factors and comprises an N-terminal receiver (response) domain and a C-terminal DNA-binding domain. In the two-component system, the sensor kinase UhpB autophosphorylates in response to a signal transduced from the membrane-associated protein UhpC (which detects external G6P). The phosphate is transferred from UhpB to UhpA, generating phosphorylated UhpA, which binds to the promoter of uhpT and activates transcription.

Expression of uhpT increases uptake of G6P into the cytoplasm, providing a carbon and phosphate source under certain environmental conditions. The UhpA regulon includes genes involved in G6P utilization, and activation is tightly regulated to prevent unnecessary uptake when G6P is absent.

Taxonomic distribution is mainly within Enterobacteriaceae; the UhpA-UhpB system has been studied extensively in E. coli K-12 and related species. It serves as a model for bacterial two-component signaling and nutrient sensing.

See also: Two-component regulatory systems; UhpB; UhpC; UhpT; Glucose-6-phosphate transport.