A molecular dynamics study of PIM₂ lipid bilayer membranes

Area of Science:

• Biophysics
• Microbiology
• Computational Biology

Background:

• The complex inner membrane of Mycobacterium tuberculosis requires simplified models for molecular dynamics simulations.
• Phosphatidyl-myo-inositol dimannosides (PIM2) are abundant lipids in the M. tuberculosis membrane, making them a suitable basis for model development.

Purpose of the Study:

• To propose and validate a minimal, single-component atomistic PIM2 bilayer model for M. tuberculosis research.
• To assess the model's ability to reproduce temperature-dependent lipid ordering and self-assembly properties.
• To investigate the interaction of the PIM2 model with the Tap (Rv1258c) efflux pump.

Main Methods:

• Atomistic molecular dynamics simulations were employed to model a PIM2 bilayer.
• The model's phase behavior was analyzed at different temperatures (310 K and 363.15 K).
• Spontaneous self-assembly and interaction with the Tap protein were simulated and compared to a standard DPPC bilayer.

Main Results:

• The PIM2 bilayer model demonstrated distinct temperature-dependent ordering regimes, exhibiting gel-like behavior at 310 K and increased fluidity at 363.15 K.
• The model showed spontaneous self-assembly into a lamellar bilayer structure, consistent with experimental observations.
• The PIM2 membrane provided a more stable environment for the Tap protein compared to a DPPC bilayer.

Conclusions:

• The proposed PIM2 bilayer is a robust and promising model for M. tuberculosis research.
• This model is well-suited for studying protein-lipid interactions relevant to multidrug resistance.
• The PIM2 model can be utilized to explore phenomena like the bacterial immunological thermostat.