EnvZ/OmpR

EnvZ/OmpR is a two-component system in Escherichia coli that regulates the expression of outer membrane proteins in response to environmental changes. The system consists of two proteins: EnvZ, a histidine kinase, and OmpR, a response regulator.

Function

The EnvZ/OmpR system is involved in the regulation of porin proteins, which are responsible for the transport of small molecules across the bacterial outer membrane. In response to changes in osmolarity, EnvZ undergoes autophosphorylation and subsequently transfers the phosphate group to OmpR. Phosphorylated OmpR then binds to the promoter regions of the porin genes, altering their expression.

EnvZ

EnvZ is a membrane-bound histidine kinase that senses changes in the environment and initiates the signal transduction pathway. It has two domains: a sensor domain located in the periplasm and a cytoplasmic kinase domain. The sensor domain detects changes in osmolarity, while the kinase domain is responsible for the autophosphorylation of EnvZ.

OmpR

OmpR is a response regulator that controls the expression of the porin genes. Upon receiving the phosphate group from EnvZ, OmpR undergoes a conformational change that allows it to bind to the promoter regions of the porin genes. The binding of OmpR to the DNA alters the transcription of the genes, leading to changes in the levels of the porin proteins.

Regulation

The EnvZ/OmpR system is regulated by changes in osmolarity. Under low osmolarity conditions, EnvZ is predominantly in a kinase state, leading to the phosphorylation of OmpR and the expression of the OmpF porin. Under high osmolarity conditions, EnvZ switches to a phosphatase state, leading to the dephosphorylation of OmpR and the expression of the OmpC porin.

See also

• Two-component system
• Histidine kinase
• Response regulator
• Porin (protein)

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