Quantitation of the phase preferences of the major lipids of the Acholeplasma laidlawii B membrane

Abstract

We have quantitated the phase preferences of all of the quantitatively significant lipids of fatty acid-homogeneous Acholeplasma laidlawii membranes by determining the effect of small amounts of each lipid on the lamellar/reversed hexagonal phase transition temperature of a phosphatidylethanolamine matrix of identical fatty acid composition using differential scanning calorimetry. We find that the incorporation of small amounts of these lipids produce effects ranging from a moderate depression to a marked elevation of the lamellar/reversed hexagonal phase transition temperature of the corresponding phosphatidylethanolamine. Thus, although the total membrane lipids from this organism form only lamellar phases under physiological conditions, the individual membrane lipids appear to exhibit a wide range of phase preferences. Phosphatidylglycerol and diglucosyldiacylglycerol seem to have relatively strong and weak preferences for the lamellar liquid-crystalline phase, respectively, while monoglucosyldiacylglycerol, and especially acyl polyprenyl glucoside, strongly prefers the reversed hexagonal phase. Most notable in this regard is the phase preference of glycerylphosphoryldiglucosyldiacylglycerol, which strongly destabilizes the reversed hexagonal phase and which we show in the accompanying paper [Lewis, R. N. A. H., & McElhaney, R. N. (1995) Biochemistry 34, 13818-13824] actually prefers the normal micellar phase in isolation. The presence of normal, lamellar, and reversed phase-preferring lipids in a single membrane has important implications for understanding the physical basis of lipid organization and biosynthetic regulation in this and possibly in other organisms. We also show that the characteristic effect of the individual A. laidlawii membrane lipids on the lamellar/reversed hexagonal phase transition temperature of the phosphatidylethanolamine matrix is not well correlated with their polar headgroup intrinsic volumes.(ABSTRACT TRUNCATED AT 250 WORDS)

The polar lipids of Clostridium psychrophilum, an anaerobic psychrophile

“…2 and 3, MGDRG is more abundant at +5 °C near the optimal growth temperature and DGDRG, which is present at −5 °C, is essentially absent at this temperature. The phase behavior of a monoglucosyldiacylglycerol (MGDG) and a diglucosyldiacylglycerol (DGDG) have been studied intensively in Acholeplasma laidlawii [27–29]. In a classic study on phase equilibria of total membrane lipids from this organism, it was shown that as the degree of unsaturation of the membrane lipids was varied from approximately 20% to over 90% cis -9–18:1 (oleic acid), the ratio of DGDG/MGDG increased from 0.59 to 5.6.…”

Comparative Genomic Analysis Revealed a Gene for Monoglucosyldiacylglycerol Synthase, an Enzyme for Photosynthetic Membrane Lipid Synthesis in Cyanobacteria

“…In the cell wall-less bacterium Acholeplasma laidlawii, MGlcDG is the most abundant lipid and occupies about one-half of its membrane (Foht et al, 1995). In Bacillus subtilis, MGlcDG is about 10% of the total lipid (Matsumoto et al, 1998).…”

Lipid Dependence and Basic Kinetics of the Purified 1,2-Diacylglycerol 3-Glucosyltransferase from Membranes of Acholeplasma laidlawii

“…The purpose is to maintain (i) phase equilibria close to a potential bilayer/nonbilayer transition (5), (ii) a nearly constant radius of spontaneous curvature (6), and (iii) a constant (anionic) surface charge density (7) for the membrane lipid bilayer mixture. Similar packing properties are also maintained in other bacteria by regulation especially at the acyl chain level, like Escherichia coli (8, 9), Clostridium butyricum (10), and Bacillus megaterium (11), the latter two also by some extent of polar head group changes.The regulation of the packing properties is mainly accomplished by altering the relative proportions of MGlcDAG and DGlcDAG, forming essentially nonlamellar and lamellar phases (5,(12)(13)(14). In vivo, parameters giving more nonlamellar properties to the bilayer, like higher growth temperature and more of longer and unsaturated acyl chains, result in an increase of the DGlcDAG fraction and a decrease of the MGlc-…”

“…The regulation of the packing properties is mainly accomplished by altering the relative proportions of MGlcDAG and DGlcDAG, forming essentially nonlamellar and lamellar phases (5,(12)(13)(14). In vivo, parameters giving more nonlamellar properties to the bilayer, like higher growth temperature and more of longer and unsaturated acyl chains, result in an increase of the DGlcDAG fraction and a decrease of the MGlc-…”