Dynamics of proteins in different solvent systems: analysis of essential motion in lipases.

We have investigated the effect of different solvents on the dynamics of Rhizomucor miehei lipase. Molecular dynamics simulations were performed in water, methyl hexanoate, and cyclohexane. Analysis of the 400-ps trajectories showed that the solvent has a pronounced effect on the geometrical properties of the protein. The radius of gyration and total accessibility surface decrease in organic solvents, whereas the number of hydrogen bonds increases. The essential motions of the protein in different solvents can be described in a low-dimensional "essential subspace," and the dynamic behavior in this subspace correlates with the polarity of the solvent. Methyl hexanoate, which is a substrate for R. miehei lipase, significantly increases the fluctuations in the active-site loop. During the simulation, a methyl hexanoate entered the active-site groove. This observation provides insight into the possible docking mechanism of the substrate.