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Journal of Bacteriology, November 2000, p. 6382-6390, Vol. 182, No. 22
Department of Biochemistry, College of
Science, Protein Network Research Center, Institute of Bioscience and
Biotechnology, Yonsei University, Seoul 120-749, Korea
Received 26 May 2000/Accepted 5 September 2000
A regulatory gene-like open reading frame oriented oppositely to
mdcL, coined mdcY, was found upstream from the structural genes of the mdcLMACDEGBH operon in Acinetobacter
calcoaceticus KCCM 40902. To elucidate the function of this gene,
mdcY was expressed in Escherichia coli, and the
MdcY protein was purified to homogeneity. Its DNA binding activity and
binding site were examined by gel retardation and footprinting assays
in vitro and by site-directed mutagenesis of the binding sites in vivo.
The regulator bound target DNA regardless of the presence of malonate,
and the binding site was found centered at
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The Malonate Decarboxylase Operon of Acinetobacter
calcoaceticus KCCM 40902 Is Regulated by Malonate and the
Transcriptional Repressor MdcY

65 relative to the
mdcL transcriptional start site and contains a 12-bp
palindromic structure (5'-ATTGTA/TACAAT-3'). Using a
promoter fusion to the reporter gene luc, we found that the
promoter PmdcY is negatively regulated by MdcY
independent of malonate. However, the promoter
PmdcL recovered its activity in the presence of
malonate. When mdcY was introduced into A. calcoaceticus KCCM 40902 in which the gene is inactivated by an
IS3 family element, malonate decarboxylase was
significantly repressed in cultures growing in acetate, succinate, or
Luria-Bertani medium. However, in cells growing in malonate, malonate
decarboxylase was induced, indicating that MdcY is a transcriptional
repressor and that malonate or a product resulting from malonate
metabolism should be the intracellular inducer of the mdc operon.
*
Corresponding author. Mailing address: Department of
Biochemistry, College of Science, Yonsei University, Seoul 120-749, Korea. Phone: 82-2-361-2699. Fax: 82-2-362-9897. E-mail:
yskim{at}yonsei.ac.kr.
Present address: Department of Anatomy and Neurobiology, University
of Maryland School of Medicine, Baltimore, MD.
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