Open AccessThe physico‐chemical characteristics of the phosphocholine‐containing glycoglycerolipid MfGL‐II govern the permeability properties of Mycoplasma fermentans
Author(s) -
BenMenachem Gil,
Byström Tomas,
Rechnitzer Hagai,
Rottem Shlomo,
Rilfors Leif,
Lindblom Göran
Publication year - 2001
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2001.02277.x
Subject(s) - phosphocholine , vesicle , membrane , chemistry , permeability (electromagnetism) , biophysics , phosphatidylglycerol , phosphatidylcholine , differential scanning calorimetry , phospholipid , lamellar structure , crystallography , chromatography , biochemistry , biology , physics , thermodynamics
Mycoplasma fermentans seems to be involved in several pathogenic condtions in humans, and is among other things capable of fusing with T‐cells and lymphocytes. The choline‐containing phosphoglycolipid 6′‐ O‐ (3″‐phosphocholine‐2″‐amino‐1″‐phospho‐1″,3″‐propanediol)‐α‐ d ‐glucopyranosyl‐(1′→3)‐1,2‐diacylglycerol (MfGL‐II) in the membrane of M. fermentans has been suggested to enhance the fusion process, and the characteristics of MfGL‐II were therefore investigated. When a cell culture ages the fraction of MfGL‐II increases, and the fraction of the other major membrane lipid, phosphatidylglycerol (PtdGro), decreases concomitantly. Swelling experiments showed that the permeability and osmotic fragility are markedly reduced in aged cells. MfGL‐II is selectively released into the surrounding medium when aged M. fermentans cells are incubated in buffer containing EDTA. The physico‐chemical properties of MfGL‐II were studied by NMR spectroscopy and differential scanning calorimetry, and they can explain the biochemical results. The temperature for the transition between gel and lamellar liquid crystalline ( L α ) phases is 35–45 °C higher for MfGL‐II than for PtdGro, which most probably gives rise to the reduced permeability in aged cells. At high water contents MfGL‐II forms an L α phase and isotropic aggregates which were interpreted to be vesicles with a radius of ≈ 450 Å. It is proposed that MfGL‐II forms vesicles in the surrounding medium when it is released from the cell membrane. Neither EDTA nor Ca 2+ ions have a significant influence on the aggregate structures formed by MfGL‐II. Our results indicate that MfGL‐II has no fusogenic properties. It is more probable that a recently identified lysolipid in the M. fermentans membrane acts as a fusogen.