Protein phosphorylation in chemotaxis and two-component regulatory systems of bacteria

Two-component regulatory systems appear to be widespread in bacteria. Phosphorylation has been demonstrated in three of the known systems and correlated with in vivo function in two cases (Che and Ntr). Although phosphorylation of sensor and regulator proteins has so far been observed exclusively in vitro, transient protein phosphorylation could provide a basis for the mechanism of signal transduction in these bacterial systems. There is currently insufficient evidence, however, to establish the precise functional relationship(s) between the conserved sensor and regulator sequences, phosphorylation, and the detailed mechanism involved in signal transduction via the sensor and regulator proteins.