MCSS functionality maps for a flexible protein.

The Multiple Copy Simultaneous Search (MCSS) methodology for finding energetically favorable positions and orientations of small functional groups in a binding site is extended to include flexibility of the target. This makes possible the finding of novel minima not present in a fixed structure and so extends the diversity of inhibitors that can be constructed starting with the MCSS procedure. Quenched molecular dynamics is used to generate energetically favorable positions and orientations of the functional groups in the field of a flexible protein. The method is applied to the viral protein HIV-1 protease with methanol and methyl ammonium as a test case. If the protein is quenched with many copies of functional groups randomly distributed in the binding site, the resulting minima have ligand-protein interaction energies that are, on average, less favorable than those obtained with standard MCSS. This is a consequence of the renormalized potential function employed in the Locally Enhanced Sampling (LES) approximation. However, local optimizations of existing MCSS minima with a flexible protein results in lower energy minima in regions of the protein that are of particular interest. Their use in constructing a consensus protein model for ligand design is discussed.