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J. Bacteriol. doi:10.1128/JB.00229-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

PdhR (pyruvate dehydrogenase complex regulator) controls the respiratory electron transport system in Escherichia coli

Department of Frontier Bioscience and Research Center for Micro-Nano Technology, Hosei University, Koganei, Tokyo 184-8584, Nippon Institute for Biological Science, Ome, Tokyo 198-0024, and Department of Advanced Bioscience, Kinki University, Nara 631-8505, Japan

^* To whom correspondence should be addressed. Email: aishiham{at}hosei.ac.jp.

	Abstract

The pyruvate dehydrogenase (PDH) multi-enzyme complex plays a key role in metabolic interconnection between glycolysis and citric acid (TCA) cycle. Transcription of the Escherichia coli genes for all three components of PDH complex in the pdhR-aceEF-lpdA operon is repressed by the pyruvate-sensing PdhR, a GntR family transcription regulator, and derepressed by pyruvate. After a systematic search for the regulation targets of PdhR using the genomic SELEX, we have identified two novel targets, ndh encoding NADH dehydrogenase II and cyoABCDE encoding cytochrome bo-type oxidase, both together forming the pathway of respiratory electron transport downstream from the PDH cycle. PDH generates NADH while Ndh and CyoABCDE together transport electrons from NADH to oxygen. Using gel-shift and DNase-I footprinting assays, the PdhR-binding site (PdhR box) was defined, which includes a palindromic consensus sequence, ATTGGTNNNACCAAT. The binding in vitro of PdhR to the PdhR box decreased in the presence of pyruvate. Promoter assays in vivo using TFP vector also indicated that the newly identified operons are repressed by PdhR and derepressed by the addition of pyruvate. Taken together we propose that PdhR is a master regulator for controlling the formation of not only the PDH complex but also the respiratory electron transport system.

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