| A spectroscopic investigation of the structure and redox properties of Escherichia coli cytochrome b-562. | |
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MedLine Citation:
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PMID: 2986699 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The six-coordinate monohaem ferricytochrome b-562 from Escherichia coli exhibits two haem-linked pH-dependent transitions detected by NMR and optical spectroscopy. Only one of these transitions, that of the Fe(III)-coordinated His-102, is detected by EPR and MCD; the ionisation of a haem propionate is not. Both ionisations are redox-state-dependent and the midpoint redox potential of the protein is markedly pH-dependent. Over the pH range 5.0 to 8.5 the potential drops from 260 mV to 110 mV and at least five single proton ionisations are responsible for this. In addition to the two spectroscopically identified ferricytochrome ionisations, there are at least three unidentified ionisations, two of which occur in the ferrous protein. From a consideration of the X-ray structure, together with NMR data, it seems probable that at least one of these ionisations involves an amino acid carboxylate. The X-ray structure also suggests that the relatively low pKa of His-102 is a result of its proximity to Arg-98. However, an appreciable interaction between these groups requires that the solution conformation differs slightly from the X-ray structure. The fast rate of electron self-exchange, over 4 X 10(6) M-1 X s-1 at 315 K and pH* 7, may be a reflection of the fact that, as shown by the X-ray structure, a large amount of the haem and axial histidine ligand are exposed at the molecular surface with an asymmetric distribution of charged groups surrounding them. |
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Authors:
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G R Moore; R J Williams; J Peterson; A J Thomson; F S Mathews |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: Biochimica et biophysica acta Volume: 829 ISSN: 0006-3002 ISO Abbreviation: Biochim. Biophys. Acta Publication Date: 1985 May |
Date Detail:
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Created Date: 1985-07-11 Completed Date: 1985-07-11 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 0217513 Medline TA: Biochim Biophys Acta Country: NETHERLANDS |
Other Details:
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Languages: eng Pagination: 83-96 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Chemical Phenomena Chemistry Circular Dichroism Cytochrome b Group / metabolism* Electron Spin Resonance Spectroscopy Escherichia coli / metabolism* Escherichia coli Proteins* Hydrogen-Ion Concentration Magnetic Resonance Spectroscopy Oxidation-Reduction Spectrophotometry |
| Chemical | |
Reg. No./Substance:
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0/Cytochrome b Group; 0/Escherichia coli Proteins; 9064-79-3/cytochrome b562, E coli |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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