Interdomain interactions within the two-component heme-based sensor DevS from Mycobacterium tuberculosis

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• DevS is a sensor in the DevS-DevR two-component system of Mycobacterium tuberculosis.
• This system regulates bacterial entry into a nonreplicating persistent state in response to environmental cues like NO and anaerobiosis.
• DevS has two GAF domains (GAF A and GAF B) and kinase/ATPase domains; GAF A binds heme for environmental sensing, but GAF B's function is unknown.

Purpose of the Study:

• To characterize the role of the GAF B domain in DevS function.
• To investigate how DevS interacts with different ligands (CO, NO, O2) and how this affects its structure and activity.
• To elucidate the mechanism of ligand discrimination by DevS.

Main Methods:

• Spectroscopic characterization (RR) of full-length DevS and truncated constructs (GAF A, GAF A/B).
• Analysis of DevS constructs in different oxidation states and bound to exogenous ligands: carbon monoxide (CO), nitric oxide (NO), and oxygen (O2).
• Comparative analysis of ligand binding and structural changes across different DevS constructs.

Main Results:

• The GAF B domain enhances the specificity of the GAF A domain's heme pocket for binding CO and NO compared to O2.
• While GAF A DevS shows two conformers for CO and NO binding, GAF A/B and full-length DevS predominantly exhibit one.
• Hydrogen bonding interactions with bound O2 are conserved across all constructs, suggesting a distinct mechanism for O2 discrimination.

Conclusions:

• DevS utilizes its GAF B domain to fine-tune ligand specificity, particularly for NO and CO sensing.
• Interactions between the two GAF domains are critical for transmitting structural changes from the heme-binding domain to the kinase domain.
• This study provides insights into the molecular mechanism of ligand discrimination and signal transduction in the DevS-DevR system, crucial for Mycobacterium tuberculosis persistence.