Monolayer black membranes from bipolar lipids of archaebacteria and their temperature-induced structural changes

Abstract

The membrane of Caldariella acidophila, an extreme thermophilic archaebacterium, is characterized by unusual bipolar complex lipids. They consist of two nonequivalent polar heads, linked by a C40 alkylic component. The molecular organization of these lipids in the plasma membrane is still a matter of study. In this paper, we present current-voltage measurements on artificial bipolar lipid membranes, indicating that molecules are indeed organized as a covalently bound bilayer, in which each molecule is completely stretched and spans its entire thickness. Furthermore, conformational transitions of these artificial membranes (which could be formed only above 70 degrees C from a lipid/squalene dispersion) are analyzed in the 80 to 15 degrees C temperature range. Abrupt variations in capacitance and valinomycin-induced conductance seem to indicate the occurrence of at least two structural changes. Measurements are also extended to different solvent systems. Results are consistent with the picture of a monolayer bipolar lipid membrane in which few solvent molecules align themselves parallel to the lipophilic chains. The amount of solvent as well as the temperature at which conformational transitions occur, depend on the solvent system in which the lipid is dispersed.

Structure of an archaeal virus capsid protein reveals a common ancestry to eukaryotic and bacterial viruses

“…Difference electron density map is contoured at 100% MCP mass content. distance of 25-30 Å for the thickness of the S. solfataricus lipid membrane (36).…”

Intact polar and core glycerol dibiphytanyl glycerol tetraether lipids in the Arabian Sea oxygen minimum zone. Part II: Selective preservation and degradation in sediments and consequences for the TEX86

“…Huguet et al, 2006c;Forster et al, 2007;Liu et al, 2009;Bijl et al, 2009). The proxy is based on the assumption that the distribution of pelagic thaumarchaeal membrane lipids changes with temperature, which has been suggested previously for other phyla of Archaea (Gliozzi et al, 1983;Gabriel and Chong, 2000;Cavicchioli, 2006), and that this signal is preserved in sediments. The temperature-dependence of the GDGT distribution was shown in mesocosms of enriched ammonia-oxidizing Archaea (AOA) (Wuchter et al, 2004;Schouten et al, 2007) as well as suspended particulate matter from marine waters <100 m depth (Wuchter et al, 2005).…”

Membrane-spanning lipids for an uncompromised monitoring of membrane fusion and intermembrane lipid transfer

“…Even archaea lacking a cell wall can survive because they contain bipolar tetraether lipids that stabilize their plasma membrane. Owing to some indirect evidence such as the absence of a preferential fracture plane on the middle of a lipid bilayer (23)(24)(25)(26)(27) and on experiments of black lipid fi lms of bipolar tetraether lipids (28)(29)(30), it is tacitly assumed that these bipolar tetraether lipids are membrane-spanning lipids (MSLs) and stretch across both leafl ets of the plasma membrane of archaea. This fact suggested using labeled derivatives of bipolar lipids as reporter molecules for an improvement of the previously discussed membrane fusion and lipid transfer assays.…”