MOLECULAR-DYNAMICS AND ELECTRON-CONFORMATIONAL INTERACTIONS IN FERREDOXIN

Numerical modeling of the molecular dynamics of Peptococcus aerogenes ferredoxin at 300 degrees K in different charge states of iron-sulfur clusters revealed a decrease as well as an increase in the mean distan ce between clusters upon protein reduction, despite that the electrost atic repulsion between them increased markedly. To describe the low-fr equency protein motions on the basis of the molecular-dynamic paths ob tained, use was made of a quasiharmonic model. The vibration spectrum for the oxidized protein was composed of two characteristic frequency bands, 1-90 and 120-200 cm(-1). The low-frequency spectrum was virtual ly insensitive to the Fe/S cluster charge state. The protein was shown to significantly affect the average structure of the Fe4S4(SH)4 compl ex, altering both its symmetry and the interatomic distances. The larg est displacements were found for SH groups (0.4 Angstrom). The deviati ons of the Fe4S4 atoms from equilibrium structure were about 0.07 Angs trom, and the change in the Fe-S bond length was insignificant (<0.005 Angstrom).