A simulation analysis of the effect of a cholesterol-dependent fusogenic peptide from HIV gp41 on membrane phospholipid dynamics

CpreTM is a fusogenic peptide whose N-terminal portion is derived from the membrane-proximal external region (MPER) and C-terminal portion covers the transmembrane (TM) domain of gp41 of HIV. CpreTM has been shown to induce membrane fusion, which requires cholesterol molecules as membrane components. To gain insight into the effects of CpreTM on membrane lipid dynamics, we performed molecular dynamics simulations. In conventional simulations, several cholesterol-binding sites were found under the segment derived from MPER and near the cholesterol recognition/interaction amino acid consensus (CRAC) motif located at the C-terminus of MPER. CpreTM resides in shallower positions in the POPC (palmitoyl oleoyl phosphatidylcholine)/cholesterol bilayer than in the pure POPC bilayer. Our metadynamic simulations using the position of one POPC molecule (“target POPC”) as the collective variable showed that CpreTM remarkably lowered the free energy cost for the POPC protrusion from the cholesterol-containing membrane; e.g., the cost for 0.7 nm outward displacement from the height of bulk POPC molecules was decreased by ~10 kJ/mol compared to the peptide-free corresponding system. Such stabilization of the POPC protrusion was not observed in the cholesterol-free POPC membrane. It was more pronounced near the aromatic residues, including the three Trp residues of CpreTM, suggesting important roles for aromatic residues in stabilizing the POPC protrusion.