FIG. 1.

Segment of sulfur metabolism in mycobacteria. Red arrows and mnemonic terms identify the activities and genes associated with the sulfur reduction operon. Dotted arrows highlight steps that are the primary focus of this study. The cysteine feedback inhibition loop is hypothesized based on similar inhibition in Salmonella enterica serovar Typhimurium (25) and E. coli (21) and complete conservation of the residues involved in the binding of cysteine (28, 29) across numerous organisms, including M. tuberculosis (29). Ac⁻, without acetyl; CoA, coenzyme A; AcCoA, acetyl coenzyme A; 3Fd(ox), oxidized ferredoxin; 3Fd_(red), reduced ferredoxin; Trx_(ox), oxidized thioredoxin; Trx_(red), reduced thioredoxin.