Biochemistry (Moscow)

, Volume 73, Issue 1, pp 14–22

Interaction of bd-type quinol oxidase from Escherichia coli and carbon monoxide: Heme d binds CO with high affinity

Authors

    • Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical BiologyLomonosov Moscow State University
Accelerated Publication

DOI: 10.1134/S0006297908010021

Cite this article as:
Borisov, V.B. Biochemistry Moscow (2008) 73: 14. doi:10.1134/S0006297908010021

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 changes in the γ-band attributable to the reaction of the ligand with 10–15% of low-spin heme b558. High-spin heme b595 does not bind CO even at high concentrations of the ligand. The apparent dissociation constant values for the heme d-CO complex of the membrane-bound and detergent-solubilized forms of the fully reduced enzyme are about 70 and 80 nM, respectively.

Key words

respiratory chainterminal oxidasecytochrome bdligand bindingcarbon monoxideenergy conservationEscherichia coli

Abbreviations

AEBSF

4-(2-aminoethyl)benzenesulfonyl fluoride

kon

second order binding rate constant

koff

dissociation rate constant

Mb

myoglobin from sperm whale skeletal muscle

MCD

magnetic circular dichroism

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© Pleiades Publishing, Ltd. 2008