ISSN:
1432-1327
Keywords:
Key words Azurin
;
Zinc cytochrome c
;
Electron transfer
;
Site-directed mutagenesis
;
Protein-protein orientation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract We study, by laser flash photolysis, the effects of ionic strength on the kinetics of the reaction 3Zncyt + az(II) → Zncyt+ + az(I), i.e., oxidative quenching of the triplet state of zinc cytochrome c by the wild-type form and the following three mutants of cupriazurin: Met44Lys, Met64Glu, and the double mutant Met44Lys/Met64Glu. Mutations in the hydrophobic patch of azurin significantly affect the reactivity of the protein with the triplet state of zinc cytochrome c. Dependence on the ionic strength of the bimolecular rate constant for the aforementioned reaction is analyzed by several electrosatic models. The two transition-state theories, Brønsted-Debye-Hückel and van Leeuwen theories, allow the best approximation to the experimental data when effective charges of the proteins are used. Protein-protein interactions are also analyzed in terms of local charges on the protein surfaces. The rate constants depend little on ionic strength, and the monopolar and dipolar electrostatic interactions between zinc cytochrome c and azurin are not well resolved. Semiquantitative analysis of electrostatic interactions indicates that azurin uses its hydrophobic patch for contact with zinc cytochrome c.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050294
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