Abstract

Bacillithiol is a compound synthesized by certain gram-positive bacteria called firmicutes, such as B. Subtilis. This compound is used to protect the bacterium from oxidative stress and establish antibiotic resistance. There are three enzymes in the synthesis pathway of bacillithiol: BshA, BshB, and BshC¹.BshC, unlike the other two, has a potentially novel mechanism that is not yet well understood. This enzyme is a putative cysteine ligase, however the ligand that donates the cysteine is unknown. The structure of BshC has been previously solved and has a unique dumbbell shape suggesting a hinging motion. Previous Small Angle X-ray Scattering (SAXS) results indicate that the structure in solution may adopt a slightly different conformation compared to the crystal structure. Using computational biochemistry methods, including molecular dynamics and normal mode analysis, we found a conformer that better fits the SAXS data and identified structural hinges. By performing structural homology searches, we were able to find potential ligands for the HUP domain Rossmann fold of the BshC active site. The results of this project will be used to formulate hypotheses about ligand interactions and possible enzyme mechanisms.