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. 2000 Dec;267(24):7224-30.
doi: 10.1046/j.1432-1327.2000.01834.x.

Identification and Characterization of a Novel Transcriptional Regulator, MatR, for Malonate Metabolism in Rhizobium Leguminosarum Bv. Trifolii

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Identification and Characterization of a Novel Transcriptional Regulator, MatR, for Malonate Metabolism in Rhizobium Leguminosarum Bv. Trifolii

H Y Lee et al. Eur J Biochem. .
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Abstract

A novel gene, matR, located upstream of matABC, transcribed in the opposite direction, and encoding a putative regulatory protein by sequence analysis was discovered from Rhizobium leguminosarum bv. trifolii. The matA, matB, and matC genes encode malonyl-CoA decarboxylase, malonyl-CoA synthetase, and a presumed malonate transporter, respectively. Together, these enzymes catalyze the uptake and conversion of malonate to acetyl-CoA. The deduced amino-acid sequence of matR showed sequence similarity with GntR from Bacillus subtilis in the N-terminal region encoding a helix-turn-helix domain. Electrophoretic mobility shift assay indicated that MatR bound to a fragment of DNA corresponding to the mat promoter region. The addition of malonate or methylmalonate increased the association of MatR and DNA fragment. DNase I footprinting assays identified a MatR binding site encompassing 66 nucleotides near the mat promoter. The mat operator region included an inverted repeat (TCTTGTA/TACACGA) centered -46.5 relative to the transcription start site. Transcriptional assays, using the luciferase gene, revealed that MatR represses transcription from the mat promoter and malonate alleviates MatR-mediated repression effect on the expression of Pmat-luc+ reporter fusion.

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