Ionic strength dependence of the non-physiological electron transfer between flavodoxin and cytochrome C553 from D. vulgaris

Sheila J. Sadeghi, Francesca Valetti, Carlos A. Cunha, Maria J. Romão, Cláudio M. Soares, Gianfranco Gilardi

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9 Citations (Scopus)

Abstract

A hypothetical model for the non-physiological electron transfer complex between cytochrome c553 (c553) and the flavodoxin (fld) from the sulphate-reducing bacteria Desulfovibrio vulgaris has been recently published [1] based on rigid-body docking and refined by molecular dynamics. In this study, the functional validity of this model is tested by looking at the role of electrostatics in the non-physiological interprotein electron transfer between the two proteins at different ionic strengths. The results are compared with the electron transfer between fld and cytochrome c from horse heart (hhc). Second-order rate constants (k2) were measured for both non-physiological systems at different ionic strengths: a complex, bell-shaped behaviour is observed for the k2 of the c553/fld redox pair with an optimum rate at I=58 mmol l-1, whereas under the same conditions the k2 for hhc/fld decreased monotonically with increasing ionic strength. Results from the electron transfer kinetics are rationalised in terms of reorganisational effects of an ensemble of conformations of the electron transfer competent c553/fld complexes, consistent with the published model.

Original languageEnglish
Pages (from-to)730-737
Number of pages8
JournalJournal of Biological Inorganic Chemistry
Volume5
Issue number6
DOIs
Publication statusPublished - 30 Nov 2000

Keywords

  • Cytochrome
  • Electron transfer
  • Electrostatic
  • Flavodoxin
  • Stopped-flow kinetics

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