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J. Bacteriol., 11 1995, 6610-6618, Vol 177, No. 22
Y Hurtubise, D Barriault, J Powlowski and M Sylvestre
In this report, we describe some of the characteristics of the Comamonas
testosteroni B-356 biphenyl (BPH)-chlorobiphenyl dioxygenase system, which
includes the terminal oxygenase, an iron-sulfur protein (ISPBPH) made up of
an alpha subunit (51 kDa) and a beta subunit (22 kDa) encoded by bphA and
bphE, respectively; a ferredoxin (FERBPH; 12 kDa) encoded by bphF; and a
ferredoxin reductase (REDBPH; 43 kDa) encoded by bphG. ISPBPH subunits were
purified from B-356 cells grown on BPH. Since highly purified FERBPH and
REDBPH were difficult to obtain from strain B-356, these two components
were purified from recombinant Escherichia coli strains by using the His
tag purification system. These His-tagged fusion proteins were shown to
support BPH 2,3- dioxygenase activity in vitro when added to preparations
of ISPBPH in the presence of NADH. FERBPH and REDBPH are thought to pass
electrons from NADH to ISPBPH, which then activates molecular oxygen for
insertion into the aromatic substrate. The reductase was found to contain
approximately 1 mol of flavin adenine dinucleotide per mol of protein and
was specific for NADH as an electron donor. The ferredoxin was found to
contain a Rieske-type [2Fe-2S] center (epsilon 460, 7,455 M-1 cm-1) which
was readily lost from the protein during purification and storage. In the
presence of REDBPH and FERBPH, ISPBPH was able to convert BPH into both
2,3-dihydro-2,3-dihydroxybiphenyl and 3,4-dihydro- 3,4-dihydroxybiphenyl.
The significance of this observation is discussed.
Copyright © 1995, American Society for Microbiology
Purification and characterization of the Comamonas testosteroni B-356 biphenyl dioxygenase components [published erratum appears in J Bacteriol 1996 Feb;178(3):943]
INRS-Sante, Institut National de la Recherche Scientifique, Pointe- Claire, Quebec, Canada.
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