Abstract Equilibrium constants for the binding of azide to ferri‐cytochrome c at temperature range‐of 305–325 K were determined at pH =7 by using 1 H double resonance method. Thermodynamic values ( ΔH° =‐34.5 kJ/mol, ΔS° =‐100 J/mol) were obtained from van't Hoff's relation and were compared with those for azide binding to other ferric hemeproteins. The reason of lower affinity of cytochrome c for azide was discussed.
Journal Article The structure of cytochrome c and its relation to recent studies of long-range electron transfer Get access Gary J. Pielak, Gary J. Pielak Search for other works by this author on: Oxford Academic PubMed Google Scholar David W. Concar, David W. Concar Search for other works by this author on: Oxford Academic PubMed Google Scholar Geoffrey R. Moore, Geoffrey R. Moore 1School of Chemical Sciences, University of East AngliaNorwich NR4 7TJ, UK Search for other works by this author on: Oxford Academic PubMed Google Scholar Robert J. P. Williams Robert J. P. Williams Search for other works by this author on: Oxford Academic PubMed Google Scholar Protein Engineering, Design and Selection, Volume 1, Issue 2, February 1987, Pages 83–88, https://doi.org/10.1093/protein/1.2.83 Published: 01 February 1987
1 H‐NMR spectroscopy has been used to measure the rate of unimolecular electron exchange between cytochrome c molecules in protein aggregates stabilised by the addition of sodium hexametaphosphate. The average intracomplex electron exchange rate is measured from line broadening of hyperfine‐shifted resonances of ferricytochrome c in an equimolar mixture of reduced and oxidised protein. The line‐broadening due to electron exchange is significantly greater than that due to protein aggregation and reaches a maximum value between 1 – 2 mol hexametaphosphate/mol protein. Significantly the exchange‐induced broadening is a first‐order process and is directly proportional to the size of the cytochrome c oligomer. From the temperature dependence of exchange broadening the activation enthalpy was estimated to be 75.8 kJ mol −1 whereas the activation entropy was 295 J mol −1 K −1 for a dimer of cytochrome c at a hexametaphosphate/protein molar ratio of 1. Both activation parameters decrease in magnitude as the order of the cytochrome c oligomer increases. The rates of intracomplex electron exchange in Saccharomyces cerevisiae iso‐2 and Candida krusei cytochromes c are lower than that of the horse protein, implying that primary sequence plays a fundamental part in determining the rate of exchange. The relevance of these observations is discussed in terms of the function of cytochrome c .
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe role of phenylalanine-82 in electron-exchange reactions of eukaryotic cytochromes cDavid W. Concar, David Whitford, Gary J. Pielak, and Robert J. P. WilliamsCite this: J. Am. Chem. Soc. 1991, 113, 7, 2401–2406Publication Date (Print):March 1, 1991Publication History Published online1 May 2002Published inissue 1 March 1991https://pubs.acs.org/doi/10.1021/ja00007a008https://doi.org/10.1021/ja00007a008research-articleACS PublicationsRequest reuse permissionsArticle Views80Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Two dimensional 1 H NMR spectroscopy is used to examine the structure and mobility of cytochrome b 5 in solution. The assignment of many residues and the interpretation of nuclear Overhauser effects (NOEs) in both redox states allow definition of secondary structural elements. Comparison with X‐ray diffraction data shows that differences between crystal and solution structures are small. The dynamics of the protein are examined and the protein is shown to be more mobile than cytochrome c . The relationship of the structure and dynamics to the electron transfer function of cytochrome b 5 is discussed.
In the presence of the highly charged hexametaphosphate anion, horse heart cytochrome c aggregates to form stable protein complexes. The formation of protein aggregates has been detected by high‐resolution 1 H‐NMR spectroscopy from an increase in the linewidth of resolved ferricytochrome c resonances with hexametaphosphate concentration. Alternatively, analytical ultracentrifugation reveals protein association from the increase in apparent sedimentation coefficients of cytochrome c in the presence of equimolar hexametaphosphate. Protein aggregation is dependent on the concentration of background electrolyte since in the range 10–150 mM sodium cacodylate alternative stabilisation of dimeric and trimeric complexes was observed by both NMR and analytical ultracentrifugation. A model is proposed for the mechanism of protein aggregation caused by polyphosphate binding to the surface of cytochrome c .
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
