Lipids archaeal

In this context it is interesting to note that archaea, which possess S-layers as exclusive cell wall components outside the cytoplasmic membrane (Fig. 14), exist under extreme environmental conditions (e.g., high temperatures, hydrostatic pressure, and salt concentrations, low pH values). Thus, it is obvious one should study the effect of proteinaceous S-layer lattices on the fluidity, integrity, structure, and stability of lipid membranes. This section focuses on the generation and characterization of composite structures that mimic the supramolecular assembly of archaeal cell envelope structures composed of a cytoplasmic membrane and a closely associated S-layer. In this biomimetic structure, either a tetraether... 

FIG. 14 Schematic illustration of an archaeal cell envelope structure (a) composed of the cytoplasmic membrane with associated and integral membrane proteins and an S-layer lattice, integrated into the cytoplasmic membrane, (b) Using this supramolecular construction principle, biomimetic membranes can be generated. The cytoplasmic membrane is replaced by a phospholipid or tetraether hpid monolayer, and bacterial S-layer proteins are crystallized to form a coherent lattice on the lipid film. Subsequently, integral model membrane proteins can be reconstituted in the composite S-layer-supported lipid membrane. (Modified from Ref. 124.)... 

Another important area of future development concerns copying the supramolecular principle of cell envelopes of archaea, which have evolved in the most extreme and hostile ecosystems. This biomimetic approach is expected to lead to new technologies for stabilizing fnnctional lipid membranes and their nse at the mesoscopic and macroscopic scales [200]. Along the same line, liposomes coated with S-layer lattices resemble archaeal cell envelopes or virns envelopes. Since liposomes have a broad application potential, particu-... 

To date, the lipids so far used have been mainly extracts from natural sources such as EPC and archaeal lipids[17,18] The chemical stability of EPC, however, is not sufficient and the membrane permeability to H1 is sometimes too high for quantitative analyses of membrane protein functions. Though archaeal lipids display many preferable features for... 

Gambacorta A, Gliozi A, De Rosa M. Archaeal lipids and their biotechnological applications. World J Microbiol Biotechnol 1995 11 115-131. 

Archaeal membranes, in contrast, contain lipids in which the hydrophobic tails are linked to the head groups by ether linkages, rather than ester linkages. Since ether linkages are more stable to heat and extremes of pH, this feature is presumed to be important to the ability of Archaea to survive in extreme environments. 

Archaeal Membranes Are Built from Ether Lipids with Branched Chains... 

Figure 12.8. Representations of Membrane Lipids. (A) Space-fdling models of a phosphoglyceride, sphingomyelin, and an archaeal lipid show their shapes and distribution of hydrophilic and hydrophobic moieties. (B) A shorthand depiction of a membrane lipid.

The existence of such a large variety of unusual lipid structures in archaea raises questions concerning the biosynthetic pathways for these lipids and their fimction in archaeal membranes, and also concerning the evolutionary relationships within the... 

The question then arises by what pathways are archaeal ether lipids biosynthesized and how were these pathways selected rather than those used by all other organisms for acyl ester lipid synthesis The available information on lipid biosynthesis in archaea is based largely, with a few exceptions, on labelling studies with whole cells (see previous reviews [4,5,9,10,13,15,85]). Biosynthetic pathways for archaeol, caldarchaeol and their complex lipid derivatives will now be discussed. 

A section on protein structural chemistry in archaea includes Chapters 5 through 7, respectively, by D. Oesterhelt on the structure and function of photoreceptor proteins in the Halobacteriaceae J. Lanyi on the structure and function of ion-transport rhodopsins in extreme halophiles and R. Hensel on proteins of extreme thermophiles. In a section on cell envelopes (Chapters 8-10), O. Kandler and H. Konig discuss the structure and chemistry of archaeal cell walls M. Kates reviews the chemistry and function of membrane lipids of archaea and L.I. Hochstein covers membrane-bound proteins (enzymes) in archaea. 

Pristane (9) (Pr) and phytane (10) (Ph) Prom chlorophylls of cyanobacteria, algae and plants bacteriochlorophylls a and b of phototrophic bacteria tocopherols Ph archaeal membrane lipids. Peters and Moldowan (1993)... 

Hopmans E. C., Schouten S., Pancost R. D., van derMeerM. J. T., and Sinninghe Damste J. S. (2000) Analysis of intact tetraether lipids in archaeal cell material and sediments using high performance liquid chromatography/atmospheric pressure ionization mass spectrometry. Rapid Common. Mass. Spectrom. 14, 585-589. 

The impressive synthetic power of the McMurry couplina was demonstrated by K. Kakinuma et al. when they synthesized archaeal 72-membered macrocyclic lipids. The final macrocyclization between the dialdehyde proceeded in 66% yield, giving rise to a single diastereomer. 

Eguchi, T., Ibaragi, K., Kakinuma, K. Total Synthesis of Archaeal 72-Membered Macrocyclic Tetraether Lipids. J. Org. Chem. 1998, 63, 2689-2698. 

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