High-Pressure Environmental Adaptation of Lipid Membranes

Abstract

The correlation between the pressure sensitivity of biological molecules and the diversity in their constituent units reveals that membrane lipids play important roles in the environmental adaptation of organisms. Bilayer membranes formed by typical membrane lipids, i.e., phospholipids, undergo phase transitions in response to changes in various external environmental factors and thereby change their membrane states. Therefore, the environmental adaptation of phospholipid bilayer membranes can be thermodynamically characterized by constructing phase diagrams with respect to bilayer phase transitions. Numerous kinds of phospholipids are found in biomembranes, and this variety is due to structural variations in each of the five functional groups (what we call “modules”) of which a single phospholipid molecule consists. By selecting a standard lipid and systematically comparing its phase diagram with those of other phospholipids whose molecular structures have been modified, it is possible to elucidate how each phospholipid bilayer adapts to its environment. In this review, we describe the temperature-pressure phase diagrams of the bilayer membranes of various phospholipids which are created by introducing various structural modifications (i.e., hydrophobic chains, chain linkage types, and polar head groups) to the standard lipid molecule in a systematic manner to discuss the the environmental adaptation of phospholipid bilayers under high pressure.

graphical abstract