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Cytochrome bd

bd-type quinol oxidases form the second family of terminal respiratory oxidases. Compared to heme-copper oxidases, cytochrome bd has a completely different structure (not yet resolved by x-ray) of the catalytic site. It lacks a copper atom and is most likely formed by two high-spin hemes: heme d and heme b595. In addition to these hemes, cytochrome bd contains a low-spin heme b558, which is directly involved in accepting electrons from quinols.

Although this oxidase does not pump protons across the membrane, it can still create ΔμH by virtue of vectorial chemistry. This results in reduced coupling efficiency which in fact turns out to have an adaptive importance for bacteria.


References:
· Borisov VB, Belevich I, Bloch DA, Mogi T, and Verkhovsky MI. (2008) Glutamate 107 in subunit I of cytochrome bd from Escherichia coli is part of a transmembrane intraprotein pathway conducting protons from cytoplasm to the heme b595/heme d active site. // Biochemistry, 47, 7907-7914. [link]
· Belevich I, Borisov VB, Verkhovsky MI. Discovery of the true peroxy intermediate in the catalytic cycle of terminal oxidases by real-time measurement. // J Biol Chem. 2007 Sep 28;282(39):28514-9 [link].
· Belevich I, Borisov VB, Bloch DA, Konstantinov AA, Verkhovsky MI. Cytochrome bd from Azotobacter vinelandii: evidence for high-affinity oxygen binding. // Biochemistry 2007 Oct 2;46(39):11177-84 [link].
· Belevich I, Borisov VB, Konstantinov AA, Verkhovsky MI. Oxygenated complex of cytochrome bd from Escherichia coli: stability and photolability. // FEBS Lett. 2005 Aug 29;579(21):4567-70 [link].
· Belevich I, Borisov VB, Zhang J, Yang K, Konstantinov AA, Gennis RB, Verkhovsky MI. Time-resolved electrometric and optical studies on cytochrome bd suggest a mechanism of electron-proton coupling in the di-heme active site. // Proc Natl Acad Sci USA. 2005 Mar 8;102(10):3657-62 [link].
· Jasaitis A, Borisov VB, Belevich NP, Morgan JE, Konstantinov AA, Verkhovsky MI.  Electrogenic reactions of cytochrome bd. // Biochemistry. 2000 Nov 14;39(45):13800-9 [link].


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