The molecular organization of nerve membranes

Zambrano, Fernando; Cellino, Marla; Canessa-Fischer, Mitzy

doi:10.1007/bf02116575

Cited by 35 publications

(7 citation statements)

References 37 publications

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“…Their most striking characteristic is the abundance of the long-chain polyunsaturated docosahexaenoic (c22:6) acid. With few exceptions, this compound seldom represents more than 10% of the fatty acids of any phosphatide, except in the nervous system where it is concentrated in the phosphatidylethanolamine and phosphatidylserine fraction of grey matter ; it is not an important component of myelin [SO] but represents about 13 % of the fatty acids in the phospholipid fraction from squid retinal axon plasma membrane [51]. However, c 2 2 : 6 is a prominent fatty acid of synaptosomal membranes from rat brain [52,53].…”

Section: Discussionmentioning

confidence: 99%

Interaction of the Acetylcholine (Nicotinic) Receptor Protein from Torpedo marmorata Electric Organ with Monolayers of Pure Lipids

Popot¹,

Demel²,

Sobel³

et al. 1978

European Journal of Biochemistry

115

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Membrane fragments rich in cholinergic (nicotinic) receptor protein were purified from the electric organ of Torpedo marmoruta. Their lipid composition is essentially characterized by the prominence of cholesterol, phosphatidylethanolamine and phosphatidylcholine, long-chain fatty acyl constituents, and the absence of sphingomyelin. Solubilised receptor was purified from these fragments and the concentration of sodium cholate lowered by dialysis to 0.01 76 (w/v). When this preparation was injected under a lipid monolayer, an increase of surface pressure developed, which was not observed with the detergent alone nor in the absence of lipid film. When covalently radiolabelled receptor preparations were injected at a constant surface pressure the radioactivity recovered with the film was proportional to the increase in area. It is concluded that the pressure or area increases are due to the penetration of the cholinergic receptor protein into the lipid film.Incorporation experiments into films formed from various pure lipids showed that the protein interacts more readily with cholesterol than with ergosterol, phosphatidylcholine, or other phospholipids. Its affinity is also higher for long-chain phosphatidylcholines than for short-chain ones. The degree of unsaturation and fluidity of the 3-sn-phosphatidylcholine (lecithin) films are of secondary importance. Parallel experiments with covalently and non-covalently labelled receptor preparations showed that part of the protein recovered with the film lost its a-toxin binding ability during the penetration.Similar data were obtained with the receptor purified from Electrophorus electricus electric organ.The acetylcholine receptor protein from fish electric organ is a well-characterized [I -41 membrane protein available in sizable quantities in a highly purified form. During the past few years several attempts have been made to incorporate the detergent-solubilized protein into artificial lipid membranes and to regain both a selective transport of cations and its regulation by nicotinic effectors (for reviews see . Because of the limited success of these attempts and their all-or-none character, several parallel approaches have been developed to circum- 250 mM NaC1, 5 mM KC1, 4 mM CaC12; 2 mM MgC12, 1.5 mM sodium phosphate buffer, pH 7.0; Ekctrophorus Ringer's solution : 160 mM NaC1, 5 mM KC1, 2 mM CaC12, 2 mM MgCl2, 2.5 mM sodium phosphate buffer, p H 7.0. Names and abbreviations for lipids follow the recent recommendations of the IUPAC-IUB Commission on Biochemical Nomenclature, see Eur. J . Biochem. 7Y, 11-21 (1977).vent the many difficulties encountered. One was to recover the binding properties [8,9] and conformational transitions [9] of the receptor protein that are strongly modified as a consequence of the detergent solubilization [S, 10-161 and/or purification. A second one is to determine if the solubilized protein carries the structure responsible for specific translocation of cations (ionophore) using specific ligands [17 -191. A third approach is to charac...

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Section: Discussionmentioning

confidence: 99%

Interaction of the Acetylcholine (Nicotinic) Receptor Protein from Torpedo marmorata Electric Organ with Monolayers of Pure Lipids

Popot¹,

Demel²,

Sobel³

et al. 1978

European Journal of Biochemistry

115

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“…Thus the lipids are derived from the axoplasm and its constituents, such as mitochondria and neurofilaments, of two morphologically distinct populations of fibers which were once myelinated but which are isolated as myelin-free entities. It is reasonable to expect that if present the axolemma would contribute a substantial amount of lipid since squid axolemma is about 50% lipid on a dry weight basis (ZAMBRANO et al, 1971) as is the rat brain synaptic plasma membrane (COTMAN et al, 1969;BRECKENRIDGE et al, 1972) which is presumably an extension of the axolemma. Table 3 has been prepared to facilitate comparison of the axonal lipids to whole white matter and two $ The values for bovine white matter and myelin were done by methods now outmoded.…”

Section: Discussionmentioning

confidence: 99%

THE LIPID COMPOSITION OF AXONS FROM BOVINE BRAIN¹

DeVries¹,

Norton²

1974

Journal of Neurochemistry

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Bovine axons derived from myelinated CNS axons were found to have 13.5% lipid. This lipid was composed of 20.1 % cholesterol, 20.1 % galactolipid, 14.6% ethanolafiine phosphatides (56.4% in the plasmalogen form), 18.3% choline phosphatides (10.0% in the plasmalogen form), 9.3% sphingomyelin, 5.6% phosphatidyl serine and 3.4% phosphatidyl inositol. The bovine axons had 033 pg ganglioside NeuNAc/mg dry weight. The axon gangliosides were found to contain the four major types of bovine gangliosides, as well as gangliosides G,, and GD3. The latter two amounted to 20.9 and 15.8 mole per cent respectively, of total gangliosides. On a molar basis, about one half of the gangliosides were monosialogangliosides. with a decreased contribution by gangliosides GT, and GD ,h relative to ganglioside distributions which have been reported for most other CNS components. The relationship of the bovine axonal lipid composition to bovine white matter and its constituents, as well as to other CNS and PNS axonal preparations is discussed.

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“…To illustrate the magnitude of the phenomenon, we consider a particular value of a. Direct analysis of the phospholipid composition of nerve membranes from both squid (Camejo et al, 1969;Zambrano et al, 1971) and garfish (Chacko et al, 1972) indicates that phosphatidyl serine alone comprises more than 10 % of the phospholipids. If we assume that 15 % of the lipids bear a negative charge, that the resting potential is 75 mV 'Eqs.…”

mentioning

confidence: 99%

Phospholipid Flip-Flop and the Distribution of Surface Charges in Excitable Membranes

McLaughlin¹,

Harary²

1974

Biophysical Journal

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There is now good evidence that most of the lipids in a biological membrane are arranged in the form of a bilayer. Charged lipids in the membrane of an excitable cell are subject to a significant driving force, the gradient of the intramembrane potential, which will tend to redistribute the lipids between the two halves of the bilayer by a "phospholipid flip-flop" mechanism. We have calculated, by combining the Boltzmann relation from statistics and the Gouy equation from the theory of the diffuse double layer, the steady-state distribution of charged lipids in the bilayer. This distribution is completely determined, within the framework of the model, by three experimentally accessible variables; the percentage of charged lipid in the bilayer as a whole, the resting potential and the ionic strength. The known values for the percentage of anionic phospholipids in squid axons (10-15%), the membrane potential (50-100 mV) and ionic strength (0.5 M) imply that the charge density and double layer potential at the outer surface of the nerve will be substantially greater than the charge density and double layer potential at the inner surface, in agreement with the best available evidence from physiological measurements.

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The molecular organization of nerve membranes

Cited by 35 publications

References 37 publications

Interaction of the Acetylcholine (Nicotinic) Receptor Protein from Torpedo marmorata Electric Organ with Monolayers of Pure Lipids

Interaction of the Acetylcholine (Nicotinic) Receptor Protein from Torpedo marmorata Electric Organ with Monolayers of Pure Lipids

THE LIPID COMPOSITION OF AXONS FROM BOVINE BRAIN¹

Phospholipid Flip-Flop and the Distribution of Surface Charges in Excitable Membranes

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The molecular organization of nerve membranes

Cited by 35 publications

References 37 publications

Interaction of the Acetylcholine (Nicotinic) Receptor Protein from Torpedo marmorata Electric Organ with Monolayers of Pure Lipids

Interaction of the Acetylcholine (Nicotinic) Receptor Protein from Torpedo marmorata Electric Organ with Monolayers of Pure Lipids

THE LIPID COMPOSITION OF AXONS FROM BOVINE BRAIN1

Phospholipid Flip-Flop and the Distribution of Surface Charges in Excitable Membranes

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THE LIPID COMPOSITION OF AXONS FROM BOVINE BRAIN¹