PMID:9888814
| Citation |
Borisov, V, Arutyunyan, AM, Osborne, JP, Gennis, RB and Konstantinov, AA (1999) Magnetic circular dichroism used to examine the interaction of Escherichia coli cytochrome bd with ligands. Biochemistry 38:740-50 |
|---|---|
| Abstract |
The interactions of the fully reduced and fully oxidized cytochrome bd from E. coli with ligands CO, NO, and CN- have been studied by a combination of absorption and magnetic circular dichroism (MCD) spectroscopy. In the reduced cytochrome bd, MCD resolves individual bands due to the high-spin heme b595 and the low-spin heme b558 components of the enzyme, allowing one to separately monitor their interactions along with ligand binding to the heme d component. The data show that at low concentrations, the ligands bind almost exclusively to heme d. At high concentrations, the ligands begin to interact with the low-spin heme b558. At the same time, no evidence for significant binding of the ligands to the high-spin heme b595 is revealed in either the reduced or the fully oxidized cytochrome bd complex. The data support the model [Borisov, V. B., Gennis, R. B., and Konstantinov, A. A. (1995) Biochemistry (Moscow) 60, 231-239] according to which the two high-spin hemes d and b595 share a high-affinity ligand binding site with a capacity for only a single molecule of the ligand; i.e., there is a strong negative cooperativity with respect to ligand binding to these two hemes with cytochrome d having an intrinsic ligand affinity much higher than that of heme b595. |
| Links |
PubMed Online version:10.1021/bi981908t |
| Keywords |
Binding Sites; Carbon Monoxide/chemistry; Circular Dichroism; Cyanates/chemistry; Cytochromes/chemistry; Electron Transport Chain Complex Proteins; Escherichia coli/enzymology; Escherichia coli Proteins; Heme/chemistry; Ligands; Magnetics; Models, Chemical; Nitric Oxide/chemistry; Oxidation-Reduction; Oxidoreductases/chemistry; Temperature |
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