Spectral properties of bacterial nitric-oxide reductase: resolution of pH-dependent forms of the active site heme b3

The Journal of Biological Chemistry
Sarah J FieldDavid J Richardson

Abstract

Bacterial nitric-oxide reductase catalyzes the two electron reduction of nitric oxide to nitrous oxide. In the oxidized form the active site non-heme Fe(B) and high spin heme b(3) are mu-oxo bridged. The heme b(3) has a ligand-to-metal charge transfer band centered at 595 nm, which is insensitive to pH over the range of 6.0-8.5. Partial reduction of nitric-oxide reductase yields a three electron-reduced state where only the heme b(3) remains oxidized. This results in a shift of the heme b(3) charge transfer band lambda(max) to longer wavelengths. At pH 6.0 the charge transfer band lambda(max) is 605 nm, whereas at pH 8.5 it is 635 nm. At pH 6.5 and 7.5 the nitric-oxide reductase ferric heme b(3) population is a mixture of both 605- and 635-nm forms. Magnetic circular dichroism spectroscopy suggests that at all pH values examined the proximal ligand to the ferric heme b(3) in the three electron-reduced form is histidine. At pH 8.5 the distal ligand is hydroxide, whereas at pH 6.0, when the enzyme is most active, it is water.

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Citations

Jun 14, 2005·Biochemical and Biophysical Research Communications·Takeshi SakuraiNobuhiko Sakurai
Apr 26, 2003·Current Opinion in Chemical Biology·Martin L Kirk, Katrina Peariso
Dec 25, 2009·Inorganic Chemistry·Jun WangKenneth D Karlin
Jun 16, 2010·The Journal of Biological Chemistry·Peter LachmannPia Adelroth
Mar 28, 2012·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·Yoshitsugu ShiroTomoya Hino
Oct 8, 2008·Proceedings of the National Academy of Sciences of the United States of America·James P CollmanEdward I Solomon
Apr 25, 2008·Methods in Enzymology·Sarah J FieldNicholas J Watmough
Jun 19, 2002·The Journal of Biological Chemistry·Robert S PitcherNicholas J Watmough
Jan 19, 2006·Biochemical Society Transactions·U FlockP Adelroth
Mar 18, 2009·Biochemical Society Transactions·Nicholas J WatmoughDavid J Richardson
Jun 16, 2006·Biochimica Et Biophysica Acta·L Mattias BlombergPer E M Siegbahn
Oct 18, 2011·Biochimica Et Biophysica Acta·Tomoya HinoYoshitsugu Shiro

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