Mechanistic studies of NO sensing and detoxificaton by bacterial iron-containing proteins

This research investigates the molecular mechanisms by which metalloproteins detect and detoxify nitric oxide (NO). We characterized two bacterial NO‑sensor proteins that use distinct metal cofactors and examined the NO dioxygenase activity of hemoglobin homologues from mammals and bacteria, a key pathway for NO detoxification. A major focus was DevS, a heme‑based sensor kinase from Mycobacterium tuberculosis that responds to CO, NO, and hypoxia by activating the DevR regulon and promoting bacterial dormancy. Using UV–visible and resonance Raman spectroscopy along with activity assays of wild‑type and variant proteins, we identified a hydrogen‑bond network involving Tyr171 that enables DevS to distinguish activating ligands (CO and NO) from inhibitory O₂. Signal transmission to the kinase domain occurs through interactions between the heme‑binding GAF‑A domain and the adjacent GAF‑B domain. These findings advance understanding of NO sensing and detoxification across biological systems.