The role of phospholipid molecular species in determining the physical properties of yeast membranes

Abstract

In most eukaryotes, including Saccharomyces cerevisiae, glycerophospholipids are the main membrane lipid constituents. Besides serving as general membrane 'building blocks', glycerophospholipids play an important role in determining the physical properties of the membrane, which are crucial for proper membrane function. To ensure optimal physical properties, membrane glycerophospholipid composition and synthesis are tightly regulated. This review will summarize our current knowledge of factors and processes determining the membrane glycerophospholipid composition of the reference eukaryote S. cerevisiae at the level of molecular species. Extrapolating from relevant model membrane data, we also discuss how modulation of the molecular species composition can regulate membrane physical properties.

Keywords: membrane fluidity; phospholipid molecular species; phospholipid properties.

Figure 1

Overview of the main phospholipid biosynthetic pathways in yeast. Enzymes involved in the synthesis of bulk PLs are indicated (in bold). ELO indicates elongation processes by Elo1p and/or Elo2p. The PS‐decarboxylation step (Psd1/2p) is the only key step not localized to ER or cytosol.

Figure 2

Homeoviscous adaptation in yeast: acyl chain composition at different growth temperatures. Wild‐type yeast cells (strain BY4741) were grown in synthetic defined glucose medium‐ to mid‐log phase at the indicated temperature. Total lipid extracts were prepared, transesterified to fatty acid methyl esters, and analyzed by GC‐FID (M. F. Renne and A. I. P.M. de Kroon, unpublished data). Data are presented as mean values ± SD (n = 3).

Figure 3

Molecular species profiles of the major membrane phospholipids in yeast. The molecular species of the main glycerophospholipids PC, PE, PS, and PI are shown of wild‐type strain BY4741, cultured to early log phase in synthetic complete glucose medium at 30 °C. Data (mean values with standard deviation; n = 3) were taken from the supplementary data of Klose et al. 12.

Figure 4

Effect of acyl chain length and unsaturation on the gel‐to‐liquid crystalline phase transition temperature (T _m) of PC and PE. T _m of completely saturated di(n:0), monounsaturated (n:0)(n:1) and diunsaturated di(n:1) PE and PC species with acyl chains containing the same number of carbons, n. Grey arrows highlight the differences in T _m between saturated, monounsaturated, and diunsaturated PC species. Data were taken from 84 for di(n:0)PC, 112 for (n:0)(n:1)PC, 113 for di(n:1)PC, and 114 for di(n:0)PE. All data were obtained by differential scanning calorimetry of lipid dispersions prepared in water. Curves were added to guide the eye.

Figure 5

The effect of the position of the cis‐double bond (Δ‐location) on the gel‐to‐liquid crystalline phase transition (T _m) of PE and PC species. All data were obtained by differential scanning calorimetry. Representative data were taken from 113 for 18:1/18:1 PC, from 115 for 18:0/18:1 PC, and 116 for 18:0/18:1 PE. Curves were fitted to guide the eye.

Figure 6

Effect of acyl chain composition on the bilayer‐to‐hexagonal phase transition temperature (T_H) of PE. All data were obtained by differential scanning calorimetry. Representative data were taken from 117 for di(n:0)PE, 118 for 18:0/18:1‐PE, and 119 for di(n:1)PE.