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Applied and Environmental Microbiology, June 2001, p. 2507-2514, Vol. 67, No. 6
Department of Microbiology, University of
Georgia, Athens, Georgia 30602
Received 7 September 2000/Accepted 12 March 2001
The bopXYZ genes from the gram-positive bacterium
Rhodococcus sp. strain 19070 encode a
broad-substrate-specific benzoate dioxygenase. Expression of the BopXY
terminal oxygenase enabled Escherichia coli to convert
benzoate or anthranilate (2-aminobenzoate) to a nonaromatic
cis-diol or catechol, respectively. This expression system
also rapidly transformed m-toluate (3-methylbenzoate) to an
unidentified product. In contrast, 2-chlorobenzoate was not a good
substrate. The BopXYZ dioxygenase was homologous to the chromosomally
encoded benzoate dioxygenase (BenABC) and the plasmid-encoded toluate
dioxygenase (XylXYZ) of gram-negative acinetobacters and pseudomonads.
Pulsed-field gel electrophoresis failed to identify any plasmid in
Rhodococcus sp. strain 19070. Catechol 1,2- and 2,3-dioxygenase activity indicated that strain 19070 possesses both
meta- and ortho-cleavage degradative pathways,
which are associated in pseudomonads with the xyl and
ben genes, respectively. Open reading frames downstream of
bopXYZ, designated bopL and bopK,
resembled genes encoding cis-diol dehydrogenases and
benzoate transporters, respectively. The bop genes were in
the same order as the chromosomal ben genes of P. putida PRS2000. The deduced sequences of BopXY were 50 to 60%
identical to the corresponding proteins of benzoate and toluate
dioxygenases. The reductase components of these latter dioxygenases,
BenC and XylZ, are 201 residues shorter than the deduced BopZ sequence.
As predicted from the sequence, expression of BopZ in E. coli yielded an approximately 60-kDa protein whose presence
corresponded to increased cytochrome c reductase activity.
While the N-terminal region of BopZ was approximately 50% identical in
sequence to the entire BenC or XylZ reductases, the C terminus was
unlike other known protein sequences.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.6.2507-2514.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Cloning and Expression of the Benzoate Dioxygenase
Genes from Rhodococcus sp. Strain 19070
*
Corresponding author. Mailing address: Department of
Microbiology, University of Georgia, Athens, GA 30602-2605. Phone:
(706) 542-2852. Fax: (706) 542-2674. E-mail:
shaddad{at}arches.uga.edu.
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