Diacylglycerol, phosphatidylserine and Ca2+: a phase behavior study

Area of Science:

• Biochemistry
• Biophysics
• Membrane Biology

Background:

• Phosphatidylserine (PS) and diacylglycerols (DAGs) are crucial lipid components in biological membranes.
• Calcium ions (Ca2+) play a significant role in modulating membrane properties and interactions.
• Understanding lipid-lipid and lipid-ion interactions is vital for deciphering membrane function.

Purpose of the Study:

• To investigate the interaction between 1,2-dipalmitoylglycerol (1,2-DPG) and dipalmitoylphosphatidylserine (DPPS).
• To elucidate the role of Ca2+ in modulating these lipid interactions and their effects on membrane phase behavior.
• To explore the implications for membrane fusion and enzyme activation.

Main Methods:

• Differential scanning calorimetry (DSC) was employed to analyze thermal phase transitions.
• 31P-nuclear magnetic resonance (31P-NMR) spectroscopy was used to determine phase structures.
• Studies were conducted in the presence and absence of Ca2+.

Main Results:

• In the absence of Ca2+, 1,2-DPG altered DPPS phase transitions and induced lipid immiscibilities at higher concentrations.
• Presence of Ca2+ further stabilized the rigid phase of DPPS/1,2-DPG mixtures and perturbed the DPPS/Ca2+ complex structure.
• 1,2-DPG enhanced the effect of Ca2+ on DPPS phase transitions, even at low 1,2-DPG concentrations.

Conclusions:

• 1,2-DPG significantly influences DPPS membrane phase behavior, with or without Ca2+.
• Ca2+ plays a critical role in stabilizing DPPS/1,2-DPG complexes, altering their structural integrity.
• These findings have implications for Ca2+-mediated membrane fusion and enzyme regulation.