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Hexameric ring structure of a thermophilic archaeon NADH oxidase that produces predominantly H 2 O
Author(s) -
Jia Baolei,
Park SeongCheol,
Lee Sangmin,
Pham Bang P.,
Yu Rui,
Le Thuy L.,
Han Sang Woo,
Yang JaeKyung,
Choi MyungSuk,
Baumeister Wolfgang,
Cheong GangWon
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06665.x
Subject(s) - random hexamer , thermophile , chemistry , protein subunit , biochemistry , stereochemistry , electron transport chain , escherichia coli , enzyme , redox , crystallography , gene , organic chemistry
An NADH oxidase (NOX) was cloned from the genome of Thermococcus profundus (NOXtp) by genome walking, and the encoded protein was purified to homogeneity after expression in Escherichia coli. Subsequent analyses showed that it is an FAD‐containing protein with a subunit molecular mass of 49 kDa that exists as a hexamer with a native molecular mass of 300 kDa. A ring‐shaped hexameric form was revealed by electron microscopic and image processing analyses. NOXtp catalyzed the oxidization of NADH and NADPH and predominantly converted O 2 to H 2 O, but not to H 2 O 2 , as in the case of most other NOX enzymess. To our knowledge, this is the first example of a NOX that can produce H 2 O predominantly in a thermophilic organism. As an enzyme with two cysteine residues, NOXtp contains a cysteinyl redox center at Cys45 in addition to FAD. Mutant analysis suggests that Cys45 in NOXtp plays a key role in the four‐electron reduction of O 2 to H 2 O, but not in the two‐electron reduction of O 2 to H 2 O 2 .