X-ray Crystallographic Structure of BshC, a Unique Enzyme Involved in Bacillithiol Biosynthesis

Bacillithiol is produced by many Gram-positive bacteria via a pathway utilizing the enzymes BshA, BshB, and BshC. Here we report the 1.77 Å resolution crystal structure of BshC, the putative cysteine ligase in bacillithiol production. The structure reveals that BshC contains a core Rossmann fold with connecting peptide motifs (CP1 and CP2) and a unique α-helical coiled-coil domain that facilitates dimerization. The model contains citrate and glycerol in the canonical active site and ADP in a second binding pocket. The overall structure and bound ligands give insight into the function of this unique enzyme.