Corynebacterium diphtheriae Methionine Sulfoxide Reductase A Exploits a Unique Mycothiol Redox Relay Mechanism

Abstract

Background: Methionine sulfoxide post-translational modifications have an important new signaling role in cells. Results: Methionine sulfoxide reductase MsrA of the pathogenic actinomycete Corynebacterium diphtheriae (Cd-MsrA) uses a unique intramolecular redox relay mechanism coupled to mycothiol. Conclusion: For methionine sulfoxide control, Cd-MsrA is flexible in receiving electrons from both the thioredoxin and the mycothiol pathways. Significance: C. diphtheriae MsrA is a redox regulator for methionine sulfoxide signaling.

The antibacterial prodrug activator Rv2466c is a mycothiol-dependent reductase in the oxidative stress response of Mycobacterium tuberculosis

“…B, the hydrogen bonding environment of the Cys 19 sulfur is depicted by black dashed lines, and the respective distances between heavy atoms are given in Å. C, by rotating the side chain of Asp 16 (the stereochemistry of this residue was also optimized using the "regularize zone" function in COOT) the carboxylate oxygen forms a close interaction with the sulfur of Cys 22 . The Rv2466c ␣-helical bundle is shown in yellow, and the thioredoxin fold is shown in orange.…”

“…Pro-154 was the only amino acid strictly conserved over the 63 sequences analyzed (according to Rv2466c numbering and thereafter), an essential residue for maintaining the Trx fold architecture (31). Residues Asp 16 and His 99 were conserved over the Rv2466c cluster (shown in salmon and deep purple in Fig. 5) in the phylogenetic analysis, although they are not present in the M. tuberculosis and C. glutamicum Mrx1 sequences (Fig.…”

“…This carboxylate moiety of Asp 23 in E. coli Trx displays an unusual high pK a of 7.58, allowing it to perform a protonation (acid) or deprotonation (base) of Cys 35 , thereby regulating the sulfur pK a reactivity (45)(46)(47). According to the active-site configuration, Asp 16 acts as a proton shuttle, deprotonating and polarizing Cys 19 or Cys 22 through its carboxylate group (Fig. 8, step 3).…”

“…Structures of reduced and oxidized Mrx1 revealed a thioredoxin fold with a CGYC catalytic site motif (11). Mrx1 activity was demonstrated with S-mycothiolated mycothiol peroxidase (Mpx) and thiol peroxidase (Tpx) from Corynebacterium glutamicum, methionine sulfoxide reductase A (MsrA) from C. glutamicum and Corynebacterium diphtheriae, and alkylhydroperoxide reductase E (AhpE) from M. tuberculosis (10,(13)(14)(15)(16).…”

Biocatalytic Preparation of Chiral Sulfoxides through Asymmetric Reductive Resolution by Methionine Sulfoxide Reductase A

“…[22] Based on the reported catalytic mechanismofM srA, the reductant was neededt ob reak the intramoleculard isulfide bond of MsrA after catalysis to regenerate the enzyme. [30][31] Thus, we intendedt oe stablish a pmMsrA regeneration system (Scheme2), aimed to prepare (R)-sulfoxide efficientlyu nder high substrate concentration. As thioredoxin (Trx) was the general reductantf or MsrA regenerationi nv ivo, [31][32] we firstly tested the effect of the pmMsrA-Trx system.T he whole-cell coexpressing pmTrxa nd pmMsrA proteins were applied to reduce the rac-1a at ac ell density of 15 gL À1 .H owever,c onversion of (S)-1a was still incomplete if the substrate concentration was higher than 8mm.A fter 10 ho fr eaction, the ee of (R)-1a was only 56 %a tasubstrate concentration of 10 mm ( Figure 2).…”