Hexameric ring structure of a thermophilic archaeon NADH oxidase that produces predominantly H2O.
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 enzymes. 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).
Jia
Baolei
B
Division of Applied Life Sciences (BK21 Program), Gyeongsang National University, Jinju, Korea.
Park
Seong-Cheol
SC
Lee
Sangmin
S
Pham
Bang P
BP
Yu
Rui
R
Le
Thuy L
TL
Han
Sang Woo
SW
Yang
Jae-Kyung
JK
Choi
Myung-Suk
MS
Baumeister
Wolfgang
W
Cheong
Gang-Won
GW
D019843:Archaeal Proteins / Q000378:metabolism*; D020134:Catalytic Domain; D003001:Cloning, Molecular; D005182:Flavin-Adenine Dinucleotide; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D019712:Thermococcus / Q000201:enzymology*; D014867:Water / Q000378:metabolism*
D019843:Archaeal Proteins; D009097:Multienzyme Complexes; D014867:Water; D005182:Flavin-Adenine Dinucleotide; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D010100:Oxygen