The sulfate effector pathway is a bacterial system dedicated to the assimilation of inorganic sulfate (SO₄²⁻) and its conversion into reduced sulfur compounds needed for the biosynthesis of essential sulfur-containing amino acids (e.g., cysteine and methionine) and cofactors. This pathway is tightly regulated by CysL, a LysR-type transcriptional regulator that responds to intracellular sulfur levels. Under sulfur-limiting conditions, CysL activates the expression of genes involved in sulfate uptake, activation, and reduction. This ensures efficient assimilation of sulfate when reduced sulfur compounds are scarce in the environment. Key genes in the CysL regulog include: Sulfate activation and reduction: sat – Encodes sulfate adenylyltransferase, which activates sulfate by converting it into adenosine 5′-phosphosulfate (APS). cysC – Encodes APS kinase, which phosphorylates APS to form 3′-phosphoadenosine 5′-phosphosulfate (PAPS), an intermediate in both assimilatory and dissimilatory sulfate reduction. cysH – Encodes PAPS reductase, which reduces PAPS to sulfite (SO₃²⁻), a key step in the assimilatory sulfate reduction pathway. cysJ and cysI – Encode the two subunits of sulfite reductase, which catalyze the final step of sulfate assimilation by reducing sulfite to sulfide (S²⁻), which can then be incorporated into cysteine. Accessory and regulatory proteins: ylnD, sirB, sirC – Likely encode accessory proteins or alternative components of the sulfite reductase complex or regulatory factors that enhance the efficiency and regulation of sulfate reduction. yjjA – Putative redox or sulfur metabolism-related gene that may contribute to maintaining the cellular redox environment during sulfur assimilation. BH3384 – A gene of unknown function, often co-regulated with sulfate reduction genes, potentially playing a supportive role in sulfur metabolism or stress response.

Sulfate References