ACCELERATED PUBLICATION 14 Interaction of bd-Type Quinol Oxidase from Escherichia coli and Carbon Monoxide: Heme d Binds CO with High Affinity

• Main Author: V B Borisov
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Sperm whale
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1039.8663; http://protein.bio.msu.ru/biokhimiya/contents/v73/pdf/bcm_0014.pdf

Cytochrome bd is a terminal quinol oxidase of the respiratory chain of aerobic and facultatively anaerobic bacteria catalyzing the four-electron reduction of molecular oxygen to water. To date, the two classes of the respiratory oxidases have been discovered. The first class comprises a numerous family of the heme/Cu-containing enzymes, which function as proton pumps and contain a binuclear oxygen-reducing active site that includes a high-spin heme and a copper ion. A typical example of the heme-copper oxidases is an aa 3 -type cytochrome c oxidase; its structural and functional defects cause serious human pathologies Cytochrome bd has no apparent homology with other known oxidases, such as cytochrome c oxidase and bo 3 -type ubiquinol oxidase The bd-type terminal oxidase is a key energy-transducing respiratory enzyme both in microorganisms harmless for humans and animals and in bacteria causing various diseases such as dysentery ACCELERATED PUBLICATION 14 Abbreviations: AEBSF) 4-(2-aminoethyl)benzenesulfonyl fluoride; k on ) second order binding rate constant; k off ) dissociation rate constant; Mb) myoglobin from sperm whale skeletal muscle; MCD) magnetic circular dichroism. Abstract-Comparative studies on the interaction of the membrane-bound and detergent-solubilized forms of the enzyme in the fully reduced state with carbon monoxide at room temperature have been carried out. CO brings about a bathochromic shift of the heme d band with a maximum at 644 nm and a minimum at 624 nm, and a peak at 540 nm. In the Soret band, CO binding to cytochrome bd results in absorption decrease and minima at 430 and 445 nm. Absorption perturbations in the Soret band and at 540 nm occur in parallel with the changes at 630 nm and reach saturation at 3-5 µM CO. The peak at 540 nm is probably either β-band of the heme d-CO complex or part of its split α-band. In both forms of cytochrome bd, CO reacts predominantly with heme d. Addition of high CO concentrations to the solubilized cytochrome bd results in additional spectral ...