The discovery of a mevalonate-independent pathway for isoprenoid biosynthesis in bacteria, algae and higher plants†

http://dosequis.colorado.edu/Courses/InsaneMembrane/papers/BR,%20HR%20and%20PRC/7electron%20crystalographic%20refinement%20of%20bacteriorhodopsin.pdf

Electron-crystallographic refinement of the structure of bacteriorhodopsin.

The role of alterations in membrane lipid composition in enabling physiological adaptation of organisms to their physical environment.

The deoxyxylulose phosphate pathway of terpenoid biosynthesis in plants and microorganisms

This review deals with the in vitro biosynthesis of the characteristics of polar lipids in archaea along with preceding in vivo studies. Isoprenoid chains are synthesized through the classical mevalonate pathway, as in eucarya, with minor modifications in some archaeal species. Most enzymes involved in the pathway have been identified enzymatically and/or genomically. Three of the relevant enzymes are found in enzyme families different from the known enzymes. The order of reactions in the phospholipid synthesis pathway (glycerophosphate backbone formation, linking of glycerophosphate with two radyl chains, activation by CDP, and attachment of common polar head groups) is analogous to that of bacteria. sn-Glycerol-1-phosphate dehydrogenase is responsible for the formation of the sn-glycerol-1-phosphate backbone of phospholipids in all archaea. After the formation of two ether bonds, CDP-archaeol acts as a common precursor of various archaeal phospholipid syntheses. Various phospholipid-synthesizing enzymes from archaea and bacteria belong to the same large CDP-alcohol phosphatidyltransferase family. In short, the first halves of the phospholipid synthesis pathways play a role in synthesis of the characteristic structures of archaeal and bacterial phospholipids, respectively. In the second halves of the pathways, the polar head group-attaching reactions and enzymes are homologous in both domains. These are regarded as revealing the hybrid nature of phospholipid biosynthesis. Precells proposed by Wachtershauser are differentiated into archaea and bacteria by spontaneous segregation of enantiomeric phospholipid membranes (with sn-glycerol-1-phosphate and sn-glycerol-3-phosphate backbones) and the fusion and fission of precells. Considering the nature of the phospholipid synthesis pathways, we here propose that common phospholipid polar head groups were present in precells before the differentiation into archaea and bacteria.

http://webpages.icav.up.pt/PTDC/CVT/098487/2008/Koga,%202007.pdf

Biosynthesis of Ether-Type Polar Lipids in Archaea and Evolutionary Considerations

On the revised structure of the major phospholipid of Halobacterium salinarium

Biosynthetic studies of the polar lipids of Halobacterium cutirubrum. Formation of isoprenyl ether intermediates

Several strains of extremely halophilic archaeobacteria, both non-alkaliphilic and alkaliphilic, including Halobacterium, Haloferax and Natronobacterium species, were isolated from salt locales in India. The major phospholipids in these strains were the C20-C20-glycerol diether analogues of phosphatidylglycerolmethylphosphate (PGP-Me), phosphatidylglycerol (PG) and phosphatidic acid (PA). In addition, the Halobacterium strains possessed the characteristic glycolipids, sulfated triglycosyl and tetraglycosyl diethers (S-TGD-1 and S-TeGD, respectively) and the unsulfated triglycosyl diether (TGD-1); and the Haloferax strains had the characteristic sulfated and unsulfated diglycosyl glycerol diethers (S-DGD-1 and DGD-1, respectively). The PGP-Me, and PG components of the haloalkaliphiles each occurred as two molecular species with C20-C20- and C20-C25- (isopranoid) glycerol diether lipid cores. In contrast to previous reports of the absence of glycolipids in natronobacteria, the Natronobacterium strains from India were found to contain small amounts of a novel glycolipid identified as glucopyranosyl-1 → 6-glucopyranosyl-1 →1-glycerol diether (DGD-4). The lipid cores of DGD-4 also contained mainly unhydroxylated or hydroxylated C20-C20, C20-C25 and C25-C25 molecular species with unsaturated (isoprenoid) chains. Hydroxylated lipid cores have previously been identified only in some methanogenic archaeobacteria.

/pdf/lipids-of-extremely-halophilic-archaeobacteria-from-saline-2vy47a2bnu.pdf

Natalia Moldoveanu

Papers

On the revised structure of the major phospholipid of Halobacterium salinarium

Biosynthetic studies of the polar lipids of Halobacterium cutirubrum. Formation of isoprenyl ether intermediates

Lipids of extremely halophilic archaeobacteria from saline environments in India: A novel glycolipid in Natronobacterium strains

Halococcus saccharolyticus sp. nov., a New Species of Extremely Halophilic Non-alkaliphilic Cocci

Polar lipids of non-alkaliphilic halococci