  This paper explores the reduced form of horse cytochrome c confined in
reverse micelles (RM) of so-dium bis-(2-ethylhexyl) sulfosuccinate (AOT) in
isooctane by molecular dynamics simulation. RMs of two sizes were constructed
at a water content of Wo = [H2O]/[AOT] = 5.5 and 9.1. Our results show that the
protein secondary structure and the heme conformation both depend on micellar
hydration. At low hydration, the protein structure and the heme moiety remain
stable, whereas at high water content the protein becomes unstable and starts
to unfold. At Wo = 9.1, according to the X-ray structure, conforma-tional
changes are mainly localized on protein loops and around the heme moiety, where
we observe a partial opening of the heme crevice. These findings suggest that
within our time window (10 ns), the structural changes observed at the heme
level are the first steps of the protein denaturation process, pre-viously
described experimentally in micellar solutions. In addition, a specific binding
of AOT molecules to a few lysine residues of the protein was found only in the
small-sized RM.
