Oxidative signaling through methionine oxidation in pathogenic Actinomycetes

Reactive oxygen species (ROS), such as hydrogen peroxide and bleach, produced by our immune system to fight off pathogenic bacteria can damage various biomolecules, including proteins. The sulfur-containing amino acid residues cysteine and methionine are the most susceptible. When methionine reacts with ROS, methionine sulfoxide is produced. Most organisms have evolved specific enzymes, methionine sulfoxide reductases (Msrs), to reverse this reaction. Such reversible sulfur-based post-translational modifications can act as regulatory on/off switches of the targeted proteins, and can signal specific oxidative stress responses. Some pathogenic bacteria, such as Mycobacterium tuberculosis, have developed a tightly controlled oxidative stress defense system to survive within macrophages. Knowledge on how these bacteria signal ROS through methionine oxidation will guide us to new target proteins and pathways for drug discovery. In this project we will employ detailed structural and functional insights in the sulfoxide-reducing enzymes MsrA and MsrB of pathogenic Actinomycetes to design new genetic probes. We will implement mutant MsrA and MsrB enzymes to specifically trap and identify sulfoxide substrate proteins at a proteome-wide scale during oxidative stress. All together, a comprehensive insight in the sulfoxome of pathogenic Actinomycetes will provide unprecedented insights in important signaling nodes of oxidative signal transduction.