Molybdate uptake interplay with ROS tolerance modulates bacterial pathogenesis

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Molybdenum is an essential trace element, functioning as a cofactor for vital molybdoenzymes across nearly all life forms.
• The ModABC transport system, utilizing the periplasmic substrate-binding protein ModA, is responsible for molybdate uptake in bacteria.

Purpose of the Study:

• To investigate the role of ModA in the growth, metabolism, and oxidative stress tolerance of Acinetobacter baumannii.
• To elucidate the structural characteristics of ModA and their impact on molybdate binding and transport.
• To assess the significance of ModA-mediated molybdate uptake in A. baumannii pathogenesis.

Main Methods:

• X-ray crystallography was employed to determine the structures of molybdate-bound ModA from A. baumannii in reduced and oxidized states.
• Biochemical assays were conducted to measure molybdate binding affinity and assess the functional impact of the disulfide bond.
• A murine pneumonia model was used to evaluate the role of ModA in A. baumannii infection.

Main Results:

• ModA was found to play critical roles in bacterial growth, metabolic pathways, and tolerance to reactive oxygen species (ROS).
• Crystal structures revealed a noncanonical disulfide bond in A. baumannii ModA, leading to conformational changes between reduced and oxidized states.
• Disulfide bond formation significantly decreased molybdate binding affinity and influenced substrate specificity, while ModA-mediated molybdate uptake was crucial for infection in a murine model.

Conclusions:

• The study highlights the structural and functional plasticity of molybdate uptake systems.
• A noncanonical disulfide bond in ModA modulates molybdate binding affinity and is important for A. baumannii virulence.
• ModA represents a potential therapeutic target for developing novel antibacterial strategies against A. baumannii infections.