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Journal of Bacteriology, July 2001, p. 4149-4156, Vol. 183, No. 14
Department of Biology and Geosciences,
Faculty of Science, Shizuoka University, Shizuoka
422-8529,1 and Department of Chemistry,
Faculty of Science, Kanazawa University, Kanazawa
920-1192,2 Japan
Received 16 January 2001/Accepted 6 April 2001
Cu-containing dissimilatory nitrite reductase (CuNiR) was purified
from denitrifying cells of a halophilic archaeon, Haloarcula marismortui. The purified CuNiR appeared blue in the oxidized state, possessing absorption peaks at 600 and 465 nm in the visible region. Electron paramagnetic resonance spectroscopy suggested the
presence of type 1 Cu (gII = 2.232;
AII = 4.4 mT) and type 2 Cu centers
(gII = 2.304; AII = 13.3 mT) in the
enzyme. The enzyme contained two subunits, whose apparent molecular
masses were 46 and 42 kDa, according to sodium dodecyl
sulfate-polyacrylamide gel electrophoresis. N-terminal amino acid
sequence analysis indicated that the two subunits were identical,
except that the 46-kDa subunit was 16 amino acid residues longer than
the 42-kDa subunit in the N-terminal region. A nirK gene
encoding the CuNiR was cloned and sequenced, and the deduced amino acid
sequence with a residual length of 361 amino acids was homologous (30 to 41%) with bacterial counterparts. Cu-liganding residues His-133,
Cys-174, His-182, and Met-187 (for type 1 Cu) and His-138, His-173, and
His-332 (for type 2 Cu) were conserved in the enzyme. As generally
observed in the halobacterial enzymes, the enzymatic activity of the
purified CuNiR was enhanced during increasing salt concentration and
reached its maximum in the presence of 2 M NaCl with the value of 960 µM NO2
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.14.4149-4156.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Purification, Characterization, and Genetic Analysis of
Cu-Containing Dissimilatory Nitrite Reductase from a Denitrifying
Halophilic Archaeon, Haloarcula marismortui

· min
1 · mg
1.
*
Corresponding author. Mailing address: Department of
Biology and Geosciences, Faculty of Science, Shizuoka University,
Shizuoka 422-8529, Japan. Phone: 81-54-238-4776. Fax: 81-54-238-0986. E-mail: sbtfuji{at}ipc.shizuoka.ac.jp.
Present address: Graduate School of Biological Sciences, Nara
Institute of Science and Technology, Takayama, Ikoma 630-0101, Japan.
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