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Highly tail-asymmetric lipids interdigitate and cause bidirectional ordering

Journal Article · · Journal of Lipid Research
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  1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
  2. National Institutes of Health (NIH), Hamilton, MT (United States)
  3. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
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Phospholipids form structurally and compositionally diverse membranes. A less studied type of compositional diversity involves phospholipid tail variety. Some phospholipids contain two acyl tails which differ in length. These tail-asymmetric lipids are shown to contribute to temperature sensitivity, oxygen adaptability, and membrane fluidity. Membranes of a highly virulent intracellular bacterium, Francisella tularensis, contain highly tail-asymmetric 1-lignoceroyl-2-decanoyl-sn-glycero-3-phosphatidylethanolamine (XJPE) lipids which were previously shown to inhibit inflammatory responses in host cells. XJPE tails have unusually high asymmetry, and how they contribute to membrane properties on a molecular level is unknown. Here, we use small angle X-ray scattering and molecular dynamics simulations to investigate how varying XJPE ratios alters properties of simple membranes. Our results demonstrate that at high concentration they promote liquid-to-gel transition in otherwise liquid membranes, while at low concentration they are tolerated well, minimally altering membrane properties. In liquid membranes, XJPE lipids dynamically adopt two main conformations; with the long tail extended into the opposing leaflet or bent-back residing in its own leaflet. When added to both leaflets XJPE primarily adopts an extended confirmation, while asymmetric addition results in more bent-back orientations. The former increases tail ordering and the latter decreases it. XJPE tails adopt different conformations that induce composition- and leaflet-dependent bidirectional effect on membrane fluidity and this suggests that Francisella tularensis could use tail asymmetry to facilitate vesicle fusion and destabilize host cells. The effect of tail-asymmetric lipids on complex membranes should be further investigated to reveal the regulatory roles of high tail asymmetry.
Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
National Institutes of Health (NIH); USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
AC02-76SF00515; AC52-07NA27344
OSTI ID:
2549461
Alternate ID(s):
OSTI ID: 2575394
OSTI ID: 2585292
Report Number(s):
LLNL-JRNL-2002279
Journal Information:
Journal of Lipid Research, Journal Name: Journal of Lipid Research Journal Issue: 5 Vol. 66; ISSN 0022-2275
Publisher:
American Society for Biochemistry and Molecular BiologyCopyright Statement
Country of Publication:
United States
Language:
English

References (1)

A Francisella tularensis Live Vaccine Strain (LVS) Mutant with a Deletion in capB , Encoding a Putative Capsular Biosynthesis Protein, Is Significantly More Attenuated than LVS yet Induces Potent Protective Immunity in Mice against F. tularensis Challenge journal October 2010

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Related Subjects

Francisella tularensis
lipids
molecular dynamics
phospholipid tail asymmetry
phospholipids
tail asymmetry