The metR binding site in the Salmonella typhimurium metH gene: DNA sequence constraints on activation.
AUTOR(ES)
Byerly, K A
RESUMO
Transcription of the metH gene in Salmonella typhimurium and Escherichia coli is positively regulated by the metR gene product, a DNA binding protein. The interaction between the MetR activator protein and the S. typhimurium metH control region was investigated. In vitro gel mobility shift assays and DNase I protection assays established that the MetR protein binds to and protects a 24-bp sequence in the metH promoter region from DNase I attack. This region includes the proposed metR recognition sequence 5'-TGAANNNNNCTCA-3'. Single-base-pair changes were introduced into the proposed MetR recognition sequence within the promoter region of a metH-lacZ gene fusion by oligonucleotide-directed mutagenesis. Two classes of mutations were identified. In the first class, the mutations caused reduced activation of the metH-lacZ fusions that correlated with reduced MetR binding. In the second class, activation of the metH-lacZ fusion was reduced, yet there was no appreciable reduction in MetR binding, indicating that the presence of bound MetR is not sufficient for activation of metH-lacZ gene expression. These two classes of mutations in the DNA binding site are grouped spatially, suggesting that the proposed MetR recognition sequence can be divided into two functional domains, one for binding and the other for activation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=207970Documentos Relacionados
- Genetic and biochemical analysis of the MetR activator-binding site in the metE metR control region of Salmonella typhimurium.
- Methionine synthesis in Escherichia coli: effect of the MetR protein on metE and metH expression.
- Characterization of a second MetR-binding site in the metE metR regulatory region of Salmonella typhimurium.
- Nucleotide sequence of the Salmonella typhimurium metR gene and the metR-metE control region.
- A new methionine locus, metR, that encodes a trans-acting protein required for activation of metE and metH in Escherichia coli and Salmonella typhimurium.