Electrostatic orientation during electron transfer between flavodoxin and cytochrome c

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Abstract
Various studies have shown that reaction rates between reversibly binding electron transfer proteins depend strongly on solution ionic strength. These observations suggest that intermolecular electrostatic interactions are important in facilitating the formation of a productive reaction complex. A recently examined system involves the reduction of vertebrate cytochrome c by bacterial flavodoxin. Although this is a nonphysiological reaction, it proceeds with rates typical for natural partners and is similarly inhibited at high ionic strengths. Here we describe computational studies which examine the role of electrostatics in the formation of a putative reaction complex between flavodoxin and cytochrome c. The results suggest that electrostatic interactions preorient the molecules before they make physical contact, facilitating the formation of an optimal reaction complex.