Biosynthesis of archaeal membrane ether lipids

Abstract

A vital function of the cell membrane in all living organism is to maintain the membrane permeability barrier and fluidity. The composition of the phospholipid bilayer is distinct in archaea when compared to bacteria and eukarya. In archaea, isoprenoid hydrocarbon side chains are linked via an ether bond to the sn-glycerol-1-phosphate backbone. In bacteria and eukarya on the other hand, fatty acid side chains are linked via an ester bond to the sn-glycerol-3-phosphate backbone. The polar head groups are globally shared in the three domains of life. The unique membrane lipids of archaea have been implicated not only in the survival and adaptation of the organisms to extreme environments but also to form the basis of the membrane composition of the last universal common ancestor (LUCA). In nature, a diverse range of archaeal lipids is found, the most common are the diether (or archaeol) and the tetraether (or caldarchaeol) lipids that form a monolayer. Variations in chain length, cyclization and other modifications lead to diversification of these lipids. The biosynthesis of these lipids is not yet well understood however progress in the last decade has led to a comprehensive understanding of the biosynthesis of archaeol. This review describes the current knowledge of the biosynthetic pathway of archaeal ether lipids; insights on the stability and robustness of archaeal lipid membranes; and evolutionary aspects of the lipid divide and the LUCA. It examines recent advances made in the field of pathway reconstruction in bacteria.

Transcriptomes of the Extremely Thermoacidophilic Archaeon Metallosphaera sedula Exposed to Metal “Shock” Reveal Generic and Specific Metal Responses

“…Fold change was calculated as 2 (LSMmetalϪLSMcontrol) . (56). The biosynthesis of isoprenoids within the Sulfolobales appears to follow the classical mevalonate pathway (57), with the initial steps being catalyzed by acetoacetyl-CoA thiolase (AACT; Msed_1647), 3-hydroxy-3-methylglutaryl-CoA synthase (HMGS; Msed_1646), and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR; Msed_1649) in converting acetyl-CoA to mevalonate.…”

Archaeosomes: an excellent carrier for drug and cell delivery

“…However, most of archaeal lipid membranes result from a mixture of lipids bearing various types of polar heads (phosphate, glycerophosphate, sugar, etc. ); moreover, several archaea organisms such as methanogens have developed mixtures of both diether and tetraether type polar lipids (Jain et al, 2014). Natural archaeal lipids extracted from representative archaea organisms that cover the scope of the archaeal lipid structures.…”

Thermococcus kodakarensis : the key to affordable biohydrogen production

“…to sn-glycerol-1-phosphate, the stereochemical opposite of the bacterial sn-glycerol-3-phosphate [542,543]. These key differences are unique to both domains and have therefore been termed "the lipid divide" [544].…”

“…Tetraether lipids form a monolayer membrane, whereas the diether lipids form a bilayer structure that closely resembles the traditional double leaflet bilayer of bacteria [110,542,543].…”

“…However, the exact route leading to tetraether synthesis is still unknown. Nevertheless, two different pathways have been postulated (Figure 5.1) [110,542,543]. In the first pathway (to which we will refer to as the traditional route), archaetidic acid is first converted to diether lipids, after which two of these molecules are coupled via a yet unknown route by a tail-to-tail condensation of the isoprenoid chains to form one tetraether molecule [542,543,[553][554][555].…”