Amphipathic-Lipid-Packing-Sensor interactions with lipids assessed by atomistic molecular dynamics

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• The Amphipathic-Lipid-Packing-Sensor (ALPS) motif is crucial for targeting proteins like ArfGAP1 to curved membranes during vesicle formation.
• ALPS specifically recognizes lipid packing defects, which are characteristic of budding vesicles in the Golgi apparatus.

Purpose of the Study:

• To investigate the microscopic interactions between the ALPS motif and phospholipid membranes with varying lipid packing densities.
• To elucidate the role of lipid packing defects in modulating ALPS motif behavior and membrane properties.

Main Methods:

• Explicit molecular dynamics (MD) simulations were employed to model ALPS-membrane interactions.
• Simulations were conducted using two distinct membrane compositions: a loosely packed dioleoylphosphatidylcholine (DOPC)/dioleoylglycerol (DOG) mixture (85:15) and a tightly packed pure DOPC membrane.

Main Results:

• The presence of DOG in the membrane induced lipid packing defects at the phosphate level, increasing headgroup hydration.
• ALPS exhibited greater conformational flexibility when embedded in the loosely packed, defect-containing membrane compared to the tightly packed membrane.
• These findings suggest that lipid packing density significantly influences ALPS motif dynamics.

Conclusions:

• Lipid packing defects, induced by DOG, alter membrane properties and enhance ALPS motif flexibility.
• The sensing of lipid packing by ALPS may be driven by entropic factors, with conformational flexibility being a key characteristic.
• This study provides insights into the molecular mechanisms underlying membrane recognition by the ALPS motif.