Modeling Protein-Micelle Systems in Implicit Water

Several membrane proteins and numerous membrane-active peptides have been studied in detergent micelles by solution NMR. However, the detailed structure of these complexes remains unknown. We propose a modeling approach that treats the protein and detergent in atomistic detail and the solvent implicitly. The model is based on previous work on dodecylphosphocholine micelles, adapted for use with the CHARMM36 force field and extended to sodium dodecyl sulfate micelles. Solvation parameters were slightly adjusted to reproduce experimental data on aggregation numbers and critical micelle concentrations. To test the approach, several membrane-active peptides and three, beta-barrel membrane proteins were subjected to molecular dynamics simulations in the presence of a large number of detergent molecules. Their experimentally determined secondary structure was maintained and the RMSD values were less than 2 angstrom. Deformations were commonly observed in the N or C termini. The atomistic view of the protein micelle systems that this approach provides could be useful in interpreting biophysical experiments carried out in the presence of detergent.