The Gene yjfQ Encodes the Repressor of the yjfR-X Regulon (ula), Which Is Involved in l-Ascorbate Metabolism in Escherichia coli

Mutations in yjfQ allowed us to identify this gene as the regulator of the operon yjfS-X (ula operon), reported to be involved in l-ascorbate metabolism. Inactivation of this gene renders constitutive the expression of the ula operon, indicating that YjfQ acts as a repressor. We also demonstrate that this repressor regulates the nearby yjfR gene, which in this way constitutes a regulon with the ula operon.