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Journal of Bacteriology, September 2001, p. 5074-5081, Vol. 183, No. 17
Department of Biological Sciences, Korea
Advanced Institute of Science and Technology, 373-1, Kusong-dong,
Yusong-gu, Taejon, 305-701, Korea
Received 3 January 2001/Accepted 29 May 2001
The aminophenol (AP) catabolic operon in Pseudomonas
putida HS12 mineralizing nitrobenzene was found to contain all
the enzymes responsible for the conversion of AP to pyruvate and acetyl
coenzyme A via extradiol meta cleavage of 2-aminophenol.
The sequence and functional analyses of the corresponding genes of
the operon revealed that the AP catabolic operon
consists of one regulatory gene, nbzR, and the following
nine structural genes, nbzJCaCbDGFEIH, which encode
catabolic enzymes. The NbzR protein, which is divergently transcribed with respect to the structural genes, possesses a leucine
zipper motif and a MarR homologous domain. It was also found that
NbzR functions as a repressor for the AP catabolic operon
through binding to the promoter region of the gene cluster in
its dimeric form. A comparative study of the AP catabolic
operon with other meta cleavage operons
led us to suggest that the regulatory unit (nbzR) was
derived from the MarR family and that the structural unit
(nbzJCaCbDGFEIH) has evolved from the ancestral
meta cleavage gene cluster. It is also proposed
that these two functional units assembled through a modular type gene
transfer and then have evolved divergently to
acquire specialized substrate specificities (NbzCaCb and NbzD) and
catalytic function (NbzE), resulting in the creation of the AP
catabolic operon. The evolutionary process of the AP operon suggests how bacteria have efficiently acquired genetic diversity and expanded their metabolic capabilities by modular type
gene transfer.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.17.5074-5081.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Genetic and Structural Organization of the Aminophenol Catabolic
Operon and Its Implication for Evolutionary Process
*
Corresponding author. Mailing address: Department of
Biological Sciences, Korea Advanced Institute of Science and
Technology, 373-1, Kusong-dong, Yusong-gu, Taejon, 305-701, Korea.
Phone: 82-42-869-2616. Fax: 82-42-869-2610. E-mail:
hskim{at}mail.kaist.ac.kr.
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