PMID:10194374

Citation	Osborne, JP, Cosper, NJ, Stälhandske, CM, Scott, RA, Alben, JO and Gennis, RB (1999) Cu XAS shows a change in the ligation of CuB upon reduction of cytochrome bo3 from Escherichia coli. Biochemistry 38:4526-32
Abstract	Copper X-ray absorption spectroscopy (XAS) has been used to examine the structures of the Cu(II) and Cu(I) forms of the cytochrome bo3 quinol oxidase from Escherichia coli. Cytochrome bo3 is a member of the superfamily of heme-copper respiratory oxidases. Of particular interest is the fact that these enzymes function as redox-linked proton pumps, resulting in the net translocation of one H+ per electron across the membrane. The molecular mechanism of how this pump operates and the manner by which it is linked to the oxygen chemistry at the active site of the enzyme are unknown. Several proposals have featured changes in the coordination of CuB during enzyme turnover that would result in sequential protonation or deprotonation events that are key to the functioning proton pump. This would imply lability of the ligands to CuB. In this work, the structure of the protein in the immediate vicinity of CuB, in both the fully oxidized and fully reduced forms of the enzyme, has been examined by Cu XAS, a technique that is particularly sensitive to changes in metal coordination. The results show that in the oxidized enzyme, CuB(II) is four-coordinate, consistent with three imidazoles and one hydroxyl (or water). Upon reduction of the enzyme, the coordination of CuB(I) is significantly altered, consistent with the loss of one of the histidine imidazole ligands in at least a substantial fraction of the population. These data add to the credibility that changes in the ligation of CuB might occur during catalytic turnover of the enzyme and, therefore, could, in principle, be part of the mechanism of proton pumping.
Links	PubMed Online version:10.1021/bi982278y
Keywords	Copper/chemistry; Copper/metabolism; Cytochromes/chemistry; Cytochromes/isolation & purification; Cytochromes/metabolism; Escherichia coli/enzymology; Escherichia coli Proteins; Histidine/chemistry; Imidazoles/chemistry; Ligands; Oxidation-Reduction; Oxidoreductases/chemistry; Oxidoreductases/metabolism; Spectrum Analysis; X-Rays
edit table

Significance

You can help EcoliWiki by summarizing why this paper is useful

Useful Materials and Methods

You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.

Annotations

<annotationlinks/>

EcoliWiki Links

Add links to pages that link here (e.g. gene, product, method pages)

References

See Help:References for how to manage references in EcoliWiki.