Site-Directed Mutagenesis of Residues within Helix VI in Subunit I of the Cytochrome bo3 Ubiquinol Oxidase from Escherichia coli Suggests That Tyrosine 288 May Be a CuB Ligand
| Autor: | Jeffrey W. Thomas, James O. Alben, Anne Puustinen, Laura J. Lemieux, Robert B. Gennis, Melissa W. Calhoun, Marten Wikstrom |
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| Rok vydání: | 1994 |
| Předmět: |
Models
Molecular Cytochrome Protein Conformation Protein subunit Molecular Sequence Data Ubiquinol oxidase Ligands Biochemistry Protein Structure Secondary Electron Transport Complex IV 03 medical and health sciences chemistry.chemical_compound Spectroscopy Fourier Transform Infrared Escherichia coli Animals Computer Simulation Amino Acid Sequence Peptide sequence Heme 030304 developmental biology 0303 health sciences Oxidase test biology Cytochrome c 030302 biochemistry & molecular biology Proton Pumps Oxygen Transmembrane domain chemistry Mutagenesis Site-Directed biology.protein Tyrosine Spectrophotometry Ultraviolet Oxidation-Reduction Copper |
| Zdroj: | Biochemistry. 33:13013-13021 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi00248a010 |
| Popis: | The heme-copper oxidase superfamily contains all of the mammalian mitochondrial cytochrome c oxidases, as well as most prokaryotic respiratory oxidases. All members of the superfamily have a subunit homologous to subunit I of the mammalian cytochrome c oxidases. This subunit provides the amino acid ligands to a low-spin heme component as well as to a heme-copper binuclear center, which is the site where dioxygen is reduced to water. The amino acid sequence of transmembrane helix VI of subunit I is the most highly conserved within the superfamily. Previous efforts have demonstrated that one of the residues in this region, H284, is critical for oxidase activity and for the assembly of CuB. This paper presents the analysis of additional site-directed mutants in which other highly conserved residues in helix VI (P285, E286, Y288, and P293) have been substituted. Most of the mutants are enzymatically inactive. Structural perturbations reported by Fourier transform infrared absorption difference spectroscopy of CO adducts of the mutant oxidases confirm the previous suggestion that this region is adjactent to CuB. Furthermore, the analysis of five different substitutions for Y288 indicates that all lack CuB. On the basis of these data, it is proposed that Y288 may be a CuB ligand along with H333, H334, and H284, and a plausible molecular model of the CuB site is presented. |
| Databáze: | OpenAIRE |
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