Roles of the GcvA and PurR proteins in negative regulation of the Escherichia coli glycine cleavage enzyme system.

AUTOR(ES)

Wilson, R L

RESUMO

When Escherichia coli was grown in medium containing both inosine and glycine, the PurR repressor protein was shown to be responsible for a twofold reduction from the fully induced glycine cleavage enzyme levels. This twofold repression was also seen by measuring beta-galactosidase levels in cells carrying a lambda gcvT-lacZ gene fusion. In this fusion, the synthesis of beta-galactosidase is under the control of the gcv regulatory region. A DNA fragment carrying the gcv control region was shown by gel mobility shift assay and DNase I footprinting to bind purified PurR protein, suggesting a direct involvement of the repressor in gcv regulation. A separate mechanism of purine-mediated regulation of gcv was shown to be independent of the purR gene product and resulted in an approximately 10-fold reduction of beta-galactosidase levels when cells were grown in medium containing inosine but lacking the inducer glycine. This additional repression was dependent upon a functional gcvA gene, a positive activator for the glycine cleavage enzyme system. A dual role for the GcvA protein as both an activator in the presence of glycine and a repressor in the presence of inosine is suggested.

Documentos Relacionados

• DNA sequence and characterization of GcvA, a LysR family regulatory protein for the Escherichia coli glycine cleavage enzyme system.
• DNA binding sites of the LysR-type regulator GcvA in the gcv and gcvA control regions of Escherichia coli.
• Positive regulation of the Escherichia coli glycine cleavage enzyme system.
• Regulation of the Escherichia coli glyA gene by the purR gene product.
• Escherichia coli purB gene: cloning, nucleotide sequence, and regulation by purR.