MtrB

mtrB is the gene encoding MtrB, a sensor histidine kinase component of the MtrAB two-component regulatory system found in several actinobacteria, notably Mycobacterium species such as M. tuberculosis and M. smegmatis. The MtrAB system functions in bacterial signal transduction, linking environmental or cellular cues to changes in gene expression.

In this system, MtrB acts as the sensor kinase. It autophosphorylates on a conserved histidine residue in response to signals detected by its N-terminal sensor domain and then transfers the phosphate to the response regulator MtrA. Phosphorylated MtrA modulates transcription of a regulon involved in processes including cell division, cell wall and envelope biogenesis, and stress responses. The exact signals and target genes can vary among species, but the pathway is generally linked to envelope integrity and replication control.

Structurally, MtrB belongs to the sensor histidine kinase family and typically contains two transmembrane helices flanking a periplasmic sensor loop, followed by cytoplasmic dimerization and histidine phosphotransfer (DHp) and catalytic/ATP-binding (CA) domains essential for autophosphorylation and phosphate transfer.

Functionally, the MtrAB system is considered essential for viability in some hosts and is a focus of tuberculosis biology and antimicrobial research. Alterations in MtrB activity influence gene expression patterns and can affect cell envelope properties and drug susceptibility, making MtrB a potential target for therapeutic intervention.

Gene context: mtrB is typically organized in an operon or gene pair with mtrA, reflecting co-regulation of sensor and response regulator.