Oxygen affinities of DosT and DosS sensor kinases with implications for hypoxia adaptation in Mycobacterium tuberculosis .

DosT and DosS are heme-based kinases involved in sensing and signaling O ₂ tension in the microenvironment of Mycobacterium tuberculosis ( Mtb ). Under conditions of low O ₂ , they activate >50 dormancy-related genes and play a pivotal role in the induction of dormancy and associated drug resistance during tuberculosis infection. In this work, we reexamine the O ₂ binding affinities of DosT and DosS to show that their equilibrium dissociation constants are 3.3±1 μM and 0.46±0.08 μM respectively, which are six to eight-fold stronger than what has been widely referred to in literature. Furthermore, stopped-flow kinetic studies reveal association and dissociation rate constants of 0.84 μM ^-1 s ^-1 and 2.8 s ^-1 , respectively for DosT, and 7.2 μM ^-1 s ^-1 and 3.3 s ^-1 , respectively for DosS. Remarkably, these tighter O ₂ binding constants correlate with distinct stages of hypoxia-induced non-replicating persistence in the Wayne model of Mtb . This knowledge opens doors to deconvoluting the intricate interplay between hypoxia adaptation stages and the signal transduction capabilities of these important heme-based O ₂ sensors.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.