A “parallel plate” electrostatic model for bimolecular rate constants applied to electron transfer proteins
Open Access
- 1 November 1994
- journal article
- research article
- Published by Wiley in Protein Science
- Vol. 3 (11), 2104-2114
- https://doi.org/10.1002/pro.5560031124
Abstract
A “parallel plate” model describing the electrostatic potential energy of protein-protein interactions is presented that provides an analytical representation of the effect of ionic strength on a bimolecular rate constant. The model takes into account the asymmetric distribution of charge on the surface of the protein and localized charges at the site of electron transfer that are modeled as elements of a parallel plate condenser. Both monopolar and dipolar interactions are included. Examples of simple (monophasic) and complex (biphasic) ionic strength dependencies obtained from experiments with several electron transfer protein systems are presented, all of which can be accommodated by the model. The simple cases do not require the use of both monopolar and dipolar terms (i.e., they can be fit well by either alone). The biphasic dependencies can be fit only by using dipolar and monopolar terms of opposite sign, which is physically unreasonable for the molecules considered. Alternatively, the high ionic strength portion of the complex dependencies can be fit using either the monopolar term alone or the complete equation; this assumes a model in which such behavior is a consequence of electron transfer mechanisms involving changes in orientation or site of reaction as the ionic strength is varied. Based on these analyses, we conclude that the principal applications of the model presented here are to provide information about the structural properties of intermediate electron transfer complexes and to quantify comparisons between related proteins or site-specific mutants. We also conclude that the relative contributions of monopolar and dipolar effects to protein electron transfer kinetics cannot be evaluated from experimental data by present approximations.Keywords
This publication has 68 references indexed in Scilit:
- A laser flash absorption spectroscopy study of Anabaena sp. PCC 7119 flavodoxin photoreduction by photosystem I particles from spinachFEBS Letters, 1992
- A comparative laser‐flash absorption spectroscopy study of algal plastocyanin and cytochrome c552 photooxidation by photosystem I particles from spinachEuropean Journal of Biochemistry, 1992
- Three-dimensional structure of p-cresol methylhydroxylase (flavocytochrome c) from Pseudomonas putida at 3.0-.ANG. resolutionBiochemistry, 1991
- Electron transfers in chemistry and biologyBiochimica et Biophysica Acta (BBA) - Reviews on Bioenergetics, 1985
- The ionic strength dependence of the rate of a reaction between two large proteins with a dipole momentBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1983
- Molecular interpretation of kinetic-ionic strength effectsJournal of Inorganic Biochemistry, 1981
- Experimental evaluation of the effective dielectric constant of proteinsJournal of Molecular Biology, 1980
- An hypothetical structure for an intermolecular electron transfer complex of cytochromes c and b5Journal of Molecular Biology, 1976
- Electric Moments of Molecules in LiquidsJournal of the American Chemical Society, 1936
- Influence of Dipole Fields between Solute Molecules. I. On Osmotic PropertiesJournal of the American Chemical Society, 1934