Activation of ATP Binding for the Autophosphorylation of DosS, a Mycobacterium tuberculosis Histidine Kinase Lacking an ATP Lid Motif

The sensor histidine kinases of Mycobacterium tuberculosis, DosS and DosT, are responsible for sensing hypoxic conditions and consist of sensor and kinase cores responsible for accepting signals and phosphorylation activity, respectively. The kinase core contains a dimerization and histidine phosphate-accepting (DHp) domain and an ATP binding domain (ABD). The 13 histidine kinase genes of M. tuberculosis can be grouped based on the presence or absence of the ATP lid motif and F box (elements known to play roles in ATP binding) in their ABDs; DosS and DosT have ABDs lacking both these elements, and the crystal structures of their ABDs indicated that they were unsuitable for ATP binding, as a short loop covers the putative ATP binding site. Although the ABD alone cannot bind ATP, the kinase core is functional in autophosphorylation. Appropriate spatial arrangement of the ABD and DHp domain within the kinase core is required for both autophosphorylation and ATP binding. An ionic interaction between Arg440 in the DHp domain and Glu537 in the short loop of the ABD is available and may open the ATP binding site, by repositioning the short loop away from the site. Mutations at Arg440 and Glu537 reduce autophosphorylation activity. Unlike other histidine kinases containing an ATP lid, which protects bound ATP, DosS is unable to accept ATP until the ABD is properly positioned relative to the histidine; this may prevent unexpected ATP reactions. ATP binding can, therefore, function as a control mechanism for histidine kinase activity. Background: Histidine kinase proteins can regulate bacterial behavior, including pathogenesis. Results: Structural and functional features of two histidine kinases of Mycobacterium tuberculosis were determined. Conclusion: Proper positioning of a short ATP lid for interaction with His phospho-accepting domain triggers ATP binding of DosS. Significance: This work describes a novel structural regulatory mechanism of histidine kinases with a short ATP lid.