In Vitro Transcriptional Studies of the bkd Operon of Pseudomonas putida: l-Branched-Chain Amino Acids and d-Leucine Are the Inducers
AUTOR(ES)
Madhusudhan, Kunapuli T.
FONTE
American Society for Microbiology
RESUMO
BkdR is the transcriptional activator of the bkd operon, which encodes the four proteins of the branched-chain keto acid dehydrogenase multienzyme complex of Pseudomonas putida. In this study, hydroxyl radical footprinting revealed that BkdR bound to only one face of DNA over the same region identified in DNase I protection assays. Deletions of even a few bases in the 5′ region of the BkdR-binding site greatly reduced transcription, confirming that the entire protected region is necessary for transcription. In vitro transcription of the bkd operon was obtained by using a vector containing the bkdR-bkdA1 intergenic region plus the putative ρ-independent terminator of the bkd operon. Substrate DNA, BkdR, and any of the l-branched-chain amino acids or d-leucine was required for transcription. Branched-chain keto acids, d-valine, and d-isoleucine did not promote transcription. Therefore, the l-branched-chain amino acids and d-leucine are the inducers of the bkd operon. The concentration of l-valine required for half-maximal transcription was 2.8 mM, which is similar to that needed to cause half-maximal proteolysis due to a conformational change in BkdR. A model for transcriptional activation of the bkd operon by BkdR during enzyme induction which incorporates these results is presented.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=93734Documentos Relacionados
- Binding of L-branched-chain amino acids causes a conformational change in BkdR.
- Transcriptional activation of the bkd operon of Pseudomonas putida by BkdR.
- Transcriptional analysis of the promoter region of the Pseudomonas putida branched-chain keto acid dehydrogenase operon.
- Characterization of BkdR-DNA binding in the expression of the bkd operon of Pseudomonas putida.
- Common Enzymes of Branched-Chain Amino Acid Catabolism in Pseudomonas putida