Nitric oxide activation by caa3 oxidoreductase from Thermus thermophilus

• Published in: Physical chemistry chemical physics : PCCP Vol. 17; no. 16; p. 10894
• Main Authors: Ohta, Takehiro, Soulimane, Tewfik, Kitagawa, Teizo, Varotsis, Constantinos
• Format: Journal Article
• Language: English
• Published: England 28-04-2015
• Subjects: Cytochrome c Group - metabolism; Cytochromes a - metabolism; Cytochromes a3 - metabolism; Heme - metabolism; Ligands; Nitric Oxide - metabolism; Thermus thermophilus - enzymology
• ISSN: 1463-9084
• DOI: 10.1039/c5cp01013f

Visible and UV-resonance Raman spectroscopy was employed to investigate the reaction of NO with cytochrome caa3 from Thermus thermophilus. We show the formation of the hyponitrite (HO-N=N-O)(-) bound to the heme a3 species (νN=N = 1330 cm(-1)) forming a high spin complex in the oxidized heme a3 Fe/CuB binuclear center of caa3-oxidoreductase. In the absence of heme a3 Fe(2+)-NO formation, the electron required for the formation of the N=N bond originates from the autoreduction of CuB by NO, producing nitrite. With the identification of the hyponitrite intermediate the hypothesis of a common phylogeny of aerobic respiration and bacterial denitrification is fully supported and the mechanism for the 2e(-)/2H(+) reduction of NO to N2O can be described with more certainty.