Molecular dynamics simulations of HIV-1 matrix-membrane interactions at different stages of viral maturation

Abstract

Although the structural rearrangement of the membrane-bound matrix (MA) protein trimers upon HIV-1 maturation has been reported, the consequences of MA maturation on the MA-lipid interactions are not well understood. Long-timescale molecular dynamics (MD) simulations of the MA multimeric assemblies of immature and mature virus particles with our realistic asymmetric membrane model have explored MA-lipid interactions and lateral organization of lipids around MA complexes. The number of stable MA-PS and MA-PIP2 interactions at the trimeric interface of the mature MA complex is observed to be greater compared to that of the immature MA complex. Our simulations identified an alternative PIP2 binding site in the immature MA complex where the multivalent headgroup of a PIP2 lipid with a greater negative charge binds to multiple basic amino acid residues such as, ARG3 residues of both the MA monomers at the trimeric interface, and HBR residues (LYS29, LYS31) of one of the MA monomers. Our enhanced sampling simulations have explored the conformational space of phospholipids at different binding sites of the trimeric interface of MA complexes. Unlike the immature MA complex, the 2 acyl tail of two PIP2 lipids at the trimeric interface of the mature MA complex is observed to sample stable binding pockets of MA consisting of helix4 residues. Together, our results provide molecular-level insights into the interactions of MA trimeric complexes with membrane and different lipid conformations at the specific binding sites of MA protein before and after viral maturation. SignificanceHIV-1 maturation facilitates the conversion of a newly formed immature virus particle to a mature infectious virion and initiates a new round of infection. The contributions of specific protein-lipid interactions in the HIV-1 assembly process are well recognized, however, the interactions of matrix protein lattice with the membrane before and after HIV-1 maturation are yet to be fully understood. Based on our simulated data, supported by prior experimental observations, the present study provides a molecular-level understanding of possible altered binding mode of PIP2 lipids after viral maturation. Identification of protein-lipid specific interactions, and lipid sorting data obtained from our long-time and large-scale atomistic MD simulations advance the understanding of the HIV-1 matrix and membrane maturation.