Isomers of glucosaminylphosphatidylglycerol

Structures, functions, and syntheses of glycero-glycophospholipids

Biological membranes consist of integral and peripheral protein-associated lipid bilayers. Although constituent lipids vary among cells, membrane lipids are mainly classified as phospholipids, glycolipids, and sterols. Phospholipids are further divided into glycerophospholipids and sphingophospholipids, whereas glycolipids are further classified as glyceroglycolipids and sphingoglycolipids. Both glycerophospholipids and glyceroglycolipids contain diacylglycerol as the common backbone, but their head groups differ. Most glycerolipids have polar head groups containing phosphate esters or sugar moieties. However, trace components termed glycero-glycophospholipids, each possessing both a phosphate ester and a sugar moiety, exist in membranes. Recently, the unique biological activities of glycero-glycophospholipids have attracted considerable attention. In this review, we describe the structure, distribution, function, biosynthesis, and chemical synthetic approaches of representative glycero-glycophospholipids-phosphatidylglucoside (PtdGlc) and enterobacterial common antigen (ECA). In addition, we introduce our recent studies on the rare glycero-glyco"pyrophospho"lipid, membrane protein integrase (MPIase), which is involved in protein translocation across biomembranes.

Cell walls of pseudomonas species sensitive to ethylenediaminetetraacetic Acid

Cell walls of 12 pseudomonads considered to be sensitive to ethylenediaminetetraacetic acid (EDTA) were prepared and analyzed. The wall of each species contained protein, peptidoglycan, loosely bound lipid, and lipopolysaccharide. The walls of Pseudomonas stutzeri and P. syncyanea were unusually susceptible to mechanical disintegration. The wall of P. syncyanea had an unusually high content of lipid and low contents of protein and peptidoglycan. Except for P. syncyanea, all the walls contained less phosphorus than the walls of the highly EDTA-sensitive P. aeruginosa and P. alcaligenes, but more than the walls of EDTA-resistant pseudomonads. The amino acid compositions of wall proteins were similar for all species. Amino sugars detected were glucosamine, galactosamine, muramic acid, and at least five unidentified components (possibly including fucosamine and quinovosamine). Glucose and rhamnose were the major neutral sugars in most walls. Galactose, mannose, fucose, and ribose were also detected, the last two each in a single species. Except for P. stutzeri and P. syncyanea, the walls had rather low contents of phospholipids (mainly cardiolipin, phosphatidylethanolamine, and phosphatidylglycerol in all species). An ornithine-containing nonphospholipid was present in all walls, and a hexuronosyldiglyceride was probably present in most walls. The fatty acid compositions of loosely bound lipids were qualitatively similar for all species: saturated C(16) and monoenoic C(16) and C(18) acids were the major components. Except for P. aureofaciens, the extraction of phosphorus on treatment of walls with EDTA at pH 9.2 was much less than for P. aeruginosa and P. alcaligenes.

The polar lipids of group B Streptococci. I. Glucosylated diphosphatidylglycerol, a novel glycopholipid

1. From group B Streptococci a novel glycophospholipid was isolated, which contained D-glucose, glycerol, acyl groups and phosphorus in a molar ratio of approx. 1:3:4:2. It was established to be 2'-O-alpha-D-glucopyranosyl-, 1',3'-bis-(1,2-diacyl-sn-glycero-3-phospho)-glycerol. 2. The structure of the deacylated core was accomplished by analyses of the breakdown products obtained on (i) strong alkaline hydrolysis, (ii) Smith-degradation, and (iii) periodate oxidation with subsequent hydrazinolysis. The four acyl groups were located by sequential degradation of the native lipid with phospholipase A2 and 98% acetic acid. 2. In group B Streptococci approximately 25% of diphosphatidylglycerol occurs in the form of its glucosylated derivative which accounts for 18% of the lipid phosphorus. The glucosylated phosphatidylglycerol analogue could not be detected. A phosphoglucolipid, however, was present, which was tentatively identified as glycerophosphodiglucosyldiacylglycerol.