Ligand binding to the haem-copper binuclear catalytic site of cytochrome bo, a respiratory quinol oxidase from Escherichia coli.
The Escherichia coli quinol oxidase, cytochrome bo, is closely related to the cytochrome-c oxidase, cytochrome aa3 and reacts with ligands to the high-spin ferric haem or the high-spin ferric-cupric binuclear catalytic site in similar ways. Cyanide reacts with the isolated enzyme to give a low-spin complex, manifested by a red shift in the Soret band, the loss of an absorption band at 630 nm and the appearance of a low-spin ferric haem EPR resonance at g = 3.3. Sulphide also elicits a low-spin complex, whereas azide gives a mixture of low-spin and high-spin species. Formate and fluoride (and azide) give a blue shift in the Soret band and the development of a modified absorption band in the 600-650 nm range. These latter species are attributed to an integral spin compound involving the binuclear centre.
Department of Biochemistry and Microbiology, University of St. Andrews, Scotland.
W J
WJ
Ingledew
J
J
Horrocks
J C
JC
Salerno
D000838:Anions; D001386:Azides / Q000378:metabolism; D001665:Binding Sites; D003300:Copper / Q000032:analysis; D003486:Cyanides / Q000378:metabolism; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D005459:Fluorides / Q000378:metabolism; D005561:Formates / Q000378:metabolism; D006418:Heme / Q000032:analysis; D008024:Ligands; D010088:Oxidoreductases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D013053:Spectrophotometry; D013440:Sulfides / Q000378:metabolism
D000838:Anions; D001386:Azides; D003486:Cyanides; D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; D005561:Formates; D008024:Ligands; D013440:Sulfides; D006418:Heme; D003300:Copper; C017168:cytochrome bo, E coli; D010088:Oxidoreductases; C020094:duroquinol oxidase; D005459:Fluorides