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 O2 tension in the microenvironment of Mycobacterium tuberculosis (Mtb). Under conditions of low O2, 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 O2 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-1s-1 and 2.8 s-1, respectively for DosT, and 7.2 μM-1s-1 and 3.3 s-1, respectively for DosS. Remarkably, these tighter O2 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 O2 sensors.