Cubic liquid crystalline phase with phosphatidyl‐ethanolamine from <i>Bacillus megaterium</i> containing branched acyl chains

Rilfors, Leif; Khan, Ali; Brentel, Ingvar; Wieslander, Åke; Lindblom, Göran

doi:10.1016/0014-5793(82)81120-4

Cited by 38 publications

(14 citation statements)

References 34 publications

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“…The molar ratio of iso/anteiso acyl chains increases more than 20-fold when the growth temperature is raised from 20 to 55 °C. This result agrees with previous observations (Rilfors et al, 1978(Rilfors et al, , 1982; however, in the present PE preparations, the increase in the acyl chain ratio is somewhat more pronounced. PE-55 does not contain any unsaturated acyl chains, while PE-20 contains about 21 mol % of monounsaturated chains (Table 1).…”

Section: Discussionsupporting

confidence: 94%

“…temperature is raised from 50 to 55 °C, the 31P NMR spectra show an increasing fraction of a narrow symmetrical signal in addition to the anisotropic spectral component. At such a low water content as 3 mol of 2H2G/mol of lipid, the narrow signal represents a reversed cubic liquid-crystalline (I2) phase (Rilfors et al, 1982;Eriksson et al, 1985a;Sjolund et al, 1987;Lindblom & Rilfors, 1989), and it was shown in earlier studies that this cubic phase is bicontinuous and belongs to the space group laid (Rilfors et al, 1982;Lindblom & Rilfors, 1989). Thus, an La phase and an I2 phase are in equilibrium between 50 and 55 °C.…”

Section: Resultsmentioning

confidence: 99%

“…PE, phosphatidylglycerol (PG), and diphosphatidylglycerol (DPG) are the dominating lipids in the membrane of B. megaterium, and PE constitutes about 55-65 mol % in the strains Ft R32 and Ot 32 within their entire growth temperature intervals (Rilfors etal., 1978). In contrast, the acyl chain composition of the membrane lipids is profoundly changed by the growth temperature (Table 1; Rilfors et al, 1978Rilfors et al, , 1982.…”

Section: Resultsmentioning

confidence: 99%

“…Isolation and Purification of Lipids. The preparation of cell membranes from B. megaterium, the extraction of the membrane lipids, and the purification of the lipid extracts were performed as described by Rilfors et al (1982). PE obtained from strain Ft R32 grown at 20 °C (PE-20) was isolated by cellulose column chromatography (Comfurius & Zwaal, 1977).…”

Section: Methodsmentioning

confidence: 99%

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Regulation and Phase Equilibria of Membrane Lipids from Bacillus megaterium and Acholeplasma laidlawii Strain A Containing Methyl-Branched Acyl Chains

Rilfors¹,

Hauksson²,

Lindblom³

1994

Biochemistry

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Phosphatidylethanolamine (PE) was isolated from Bacillus megaterium grown at 20 and 55 degrees C (PE-20 and PE-55). Iso and anteiso methyl-branched, saturated acyl chains are predominant in B. megaterium, and the value of the molar ratio of iso/anteiso acyl chains is more than 20-fold higher in PE-55 than in PE-20. Moreover, about 21 mol% of the acyl chains of PE-20 are monounsaturated. The phase equilibria differ between the two PE preparations: (1) PE-20 is more prone to form reversed nonlamellar phases than PE-55; (2) PE-20 forms both reversed cubic (I2) and reversed hexagonal (H(II)) phases while PE-55 forms only an HII phase; and (3) the lamellar liquid-crystalline (L alpha) phase of PE-20 takes up about 70% more water than the L alpha phase of PE-55. These differences can be explained by the differences in the acyl chain composition. When the growth temperature is raised, PE molecules with a reduced tendency to form nonlamellar phases are probably synthesized by B. megaterium in order to counteract the bilayer destabilizing effect of the temperature. The regulation of the acyl chain composition is not needed in order to regulate the temperature for the transition between gel/crystalline and L alpha phases of the membrane lipids. Acholeplasma laidlawii strain A-EF22 was grown at 37 degrees C on 15-(1,1,1(-2) H3)methylhexadecanoic acid, 14-(1,1,1(-2)H3)methylhexadecanoic acid or 13-(1,1,1(-2)H3)methylhexadecanoic acid, and these acids constituted 84-89 mol% of the acyl chains in the membrane lipids. The molar ratio between the two dominating lipids, monoglucosyldiacylglycerol (MGLcDAG) and diglucosyldiacylglycerol (DGlcDAG), decreased, and the molar fraction of the anionic lipids increased, when the methyl branch was moved from position 15 to position 13. Concomitantly, the order of the methyl branch increased in cells as well as in total lipid extracts. The phase equilibria of total lipid extracts (neutral lipids removed) were studied with 20 wt % of water, and HII and I2 phases were formed above 63-67 degrees C. These results indicate that the regulation of the polar head-group composition compensates for the difference in acyl chain packing introduced into the bilayer by the three branched-chain fatty acids. The regulation of the polar head-group composition of the A. laidlawii lipids cannot regulate the temperature for the transition between gel/crystalline and L alpha phases of the lipids, i.e. the transition to fluid acyl chains.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Discussionsupporting

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Regulation and Phase Equilibria of Membrane Lipids from Bacillus megaterium and Acholeplasma laidlawii Strain A Containing Methyl-Branched Acyl Chains

Rilfors¹,

Hauksson²,

Lindblom³

1994

Biochemistry

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“…Specifically, the phase boundaries are deter-phosphatidylcholine/bile salt (BS) mixtures (4, 5, 10, 13, mined by the spontaneous curvature of the monolayers. We show 14), the kinetics and mechanisms of phase transformation that because the phase boundaries are apparently independent of (12, 15,16), the nature of the interactions in these systems ionic strength, the influence of ionic strength on the spontaneous (10,(17)(18)(19), and the structure of the PC/BS mixed assemcurvature is negligible in comparison to the main value determined blies (11,(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). Yet, several basic issues remain unclear Key Words: phospholipids; bile salts; vesicles; mixed micelles; fect both the phase behavior of the mixed systems and the ionic strength.…”

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confidence: 98%