The molybdate effector pathway is essential for the uptake and regulation of molybdate ions (MoO₄²⁻), which are required for the biosynthesis of molybdenum cofactors (MoCo)—key components of various redox enzymes such as nitrate reductases, formate dehydrogenases, and xanthine oxidases. This pathway is regulated by ModE, a molybdate-responsive transcriptional regulator. ModE senses intracellular molybdate levels and modulates gene expression accordingly. In the presence of molybdate, ModE binds molybdate ions and acts as a repressor, binding to the promoters of target genes and inhibiting transcription to prevent excess molybdate uptake. Under molybdate-limiting conditions, ModE repression is relieved, and expression of molybdate transport genes is activated. Key genes in the ModE regulog include: modA – Encodes the periplasmic molybdate-binding protein of the ModABC transporter complex, which captures molybdate from the environment. modB – Encodes the membrane permease component of the transporter, facilitating molybdate translocation across the inner membrane. modC – Encodes the ATP-binding cassette (ABC) transporter ATPase, which hydrolyzes ATP to power active molybdate import.

Molybdate References