Membrane Properties of Archæal Macrocyclic Diether Phospholipids

Abstract

Several biophysical properties of four synthetic archñal phospholipids [one polyprenyl macrocyclic lipid A and three polyprenyl double-chain lipids (B, C, D) bearing zero, one or four double bonds in each chain] were studied using differential scanning calorimetry, electron and optical microscopies, stopped-flow/light scattering and solidstate 2 H-NMR techniques. These phospholipids gave a variety of self-organized structures in water, in particular vesicles and tubules. These assemblies change in response to simple thermal convection. Some specific membrane properties of these archñal phospholipids were observed: They are in a liquidcrystalline state over a wide temperature range; the dynamics of their polyprenyl chains is higher than that of n-acyl chains; the water permeability of the membranes is lower than that of n-acyl phospholipid membranes. It was also found that macrocyclization remarkably improves the barrier properties to water and the membrane stability. This may be related to the adaptation of Methanococcus jannaschii to the extreme conditions of the deep-sea hydrothermal vents.

Functionalized Membrane Domains: An Ancestral Feature of Archaea?

“…Indeed, the presence of an intramolecular C-C bond may limit the independent motions of the two alkyl chains of the tetraethers in addition to crowding the membrane internal space, enhancing membrane packing and creating an effective barrier to water and ion fluxes. Such an effect has been demonstrated for macrocyclic diether lipids, which have a structure resembling that of GMGT, with a C-C bond linking the two phytanyl chains (Dannenmuller et al, 2000). The relative abundance of GMGT (41%) in T. waiotapuensis, one of the few strains isolated from a terrestrial hot spring, suggests that these core structures may have played a critical role in the transition from marine hydrothermal vents to continental freshwater hydrothermal systems.…”

Specific Partial Reduction of Geranylgeranyl Diphosphate by an Enzyme from the Thermoacidophilic Archaeon Sulfolobus acidocaldarius Yields a Reactive Prenyl Donor, Not a Dead-End Product

“…(All-E)-farnesyl diphosphate was donated by Kyozo Ogura and Tanetoshi Koyama, Tohoku University. Nonlabeled isopentenyl diphosphate (IPP) was donated by C. Ohto, Toyota Motor Co. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]IPP was purchased from GE Healthcare, United Kingdom. Nonlabeled GGPP, GGGP, and DGGGP were synthesized enzymatically from farnesyl diphosphate, IPP, and racemic glyceryl-1-phosphate, as previously described (10).…”

“…One of the modifications-the complete reduction of double bonds in the isoprenoid chains-is thought to be important for the survival of archaea under extreme conditions, such as high temperature, because the existence of double bonds affects the properties of the membrane (6). The archaeal enzyme that catalyzes the reduction of geranylgeranyl groups in lipid precursors, geranylgeranyl reductase (GGR), was recently found in two thermophilic euryarchaeotes, Thermoplasma acidophilum (20) and Archaeaoglobus fulgidus (16).…”

Microbial Diversity and Biosignatures: An Icy Moons Perspective

“…The adaptation of the archaeal membrane to extreme environments may be attributed in part to the specific structure of its lipids. Although membranes consisting of fatty acyl ester lipids are in the gel phase or liquid crystal phase according to their fatty acid composition, it is presumed that Archaeal polar lipid membranes of archaeol and caldarchaeol are in the liquid crystal phase over a wide temperature range of 0-100°C (Stewart et al 1990;Dannenmuller et al 2000).…”