Ligand Binding in a Docking Site of Cytochrome c Oxidase: A Time-Resolved Step-Scan Fourier Transform Infrared Study
| Autor: | Tewfik Soulimane, Constantinos Varotsis, Constantinos Koutsoupakis |
|---|---|
| Přispěvatelé: | Βαρώτσης, Κωνσταντίνος, Κουτσουπάκης, Κωνσταντίνος |
| Rok vydání: | 2003 |
| Předmět: |
Stereochemistry
Infrared spectroscopy Heme Ligands Biochemistry Cytochrome oxidase Catalysis Electron Transport Complex IV chemistry.chemical_compound Colloid and Surface Chemistry Bacterial Proteins Spectroscopy Fourier Transform Infrared Cytochrome c oxidase Binding site Carbon monoxide chemistry.chemical_classification Carbon Monoxide Binding Sites Photolysis biology Thermus thermophilus Fourier transform infrared spectroscopy General Chemistry Ligand (biochemistry) Small molecule Enzymes chemistry Docking (molecular) biology.protein Propionate Engineering and Technology Ligand binding (Biochemistry) Dissociation |
| Zdroj: | Journal of the American Chemical Society. 125:14728-14732 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The description of reaction regulation in enzymes responsible for activating and catalyzing small molecules (O(2), NO) requires identification of ligand movement into the binding site and out of the enzyme through specific channels and docking sites. We have used time-resolved step-scan Fourier transform infrared spectroscopy on CO-photolyzed cytochrome c oxidase ba(3) from T. thermophilus, which is responsible for the activation and reduction of both O(2) and NO, to gain insight into the structure of ligand-binding intermediates at ambient temperature. We show that, upon dissociation, the photolyzed CO becomes trapped within a ligand docking site located near the ring A propionate of heme a(3). The 2131 cm(-1) mode of the "docked" CO we have detected corresponds to the B(1) state of Mb and persists for 35 micros. The release of CO from the docking site is not followed by recombination to the heme a(3) Fe. Our analysis indicates that this behavior reflects a mechanism in which the protein near ring A of heme a(3) propionate reorganizes about the released CO from the docking site, and establishes a transient barrier that inhibits the recombination process to the heme a(3) Fe for a few milliseconds. Rebinding to heme a(3) occurs with k(2) = 29.5 s(-1). These results have implications for understanding the role of ligand binding/escape through docking sites and channels in heme-copper oxidases and, thus, in respiration. |
| Databáze: | OpenAIRE |
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