The sensor kinase TodS operates by a multiple step phosphorelay mechanism involving two autokinase domains.

ABSTRACT: Expression of the Pseudomonas putida tod operon, which encodes enzymes for toluene metabolism, takes place from the P(todX) promoter and is mediated by the TodS/TodT two component system. The sensor kinase TodS has a complex domain arrangement containing two functional modules, each harboring a sensor- and an autokinase domain and separated by a receiver domain. Based on site-directed mutagenesis of phosphoaccepting His-190, Asp-500, and His-760 and in vitro transphosphorylation experiments with recombinant TodS fragments, we show that TodS uses a multiple step phosphorelay mechanism to activate TodT. Toluene binding stimulates exclusively phosphorylation of His-190, which is followed by phosphotransfer to Asp-500 and subsequently to His-760 prior to phosphorylation of TodT Asp-57. Mutation of His-190, Asp-500, and H760A prevented up-regulation of toluene-mediated stimulation of TodT transphosphorylation in vitro and reduced in vivo expression of P(todX) to the basal level. Calorimetric studies support that TodT binds to the C-terminal kinase module with a K(D) of approximately 200 nm and 1:1 stoichiometry. This is the first report of a multiple step phosphorelay mechanism of a sensor kinase that involves two autokinase domains.

SUBMITTER: Busch A 

PROVIDER: S-EPMC2667722 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature