A study on the topological distribution of phospholipids in microsomal membranes of chick brain using phospholipase C and trinitrobenzenesulfonic acid

• Published in: Biochimica et biophysica acta Vol. 734; no. 2; pp. 257 - 266
• Main Authors: DOMINSKI, J, BINAGLIA, L, DREYFUS, H, MASSARELLI, R, MERSEL, M, FREYSZ, L
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 12.10.1983; North-Holland
• Subjects: Animals; Biological and medical sciences; Brain - ultrastructure; Chickens; Fundamental and applied biological sciences. Psychology; Intracellular Membranes - metabolism; Microsomes - drug effects; Microsomes - metabolism; Molecular and cellular biology; Nitrobenzenes - pharmacology; Phospholipases - metabolism; Phospholipids - metabolism; Time Factors; Tissue Distribution; Trinitrobenzenesulfonic Acid - pharmacology; Type C Phospholipases - metabolism; Molecular arrangement; Phospholipase; Vertebrata; Asymmetry; Distribution; Phospholipid; Brain (Vertebrata); Biomembrane; Chicken; Aves; Microsome
• ISSN: 0006-3002; 1878-2434
• DOI: 10.1016/0005-2736(83)90123-2

The transbilayer distribution of phospholipids in chicken brain microsomal membranes has been investigated using trinitrobenzenesulfonic acid and phospholipase C from Clostridium welchii. The exposure of intact microsomes to trinitrobenzenesulfonic acid showed that the labelling of aminophospholipids followed biphasic kinetics, indicating that these membranes contain a fast- and a slow-reacting pool of aminophospholipids. Use of microsomes radioiodinated on their surface led to the conclusion that the fast-reacting pool may be located on the outer leaflet of the microsomal vesicles. It contains about 35% of the phosphatidylethanolamine, 29% of the ethanolamine plasmalogens and 18% of the phosphatidylserine. The treatment of intact microsomes with the phospholipase C Cl. welchii produced the hydrolysis of 50% of the phospholipids without any loss of their permeability properties, indicating that they are not permeable to the hydrolase. Phospholipids extracted from the microsomes were hydrolyzed rapidly by the phospholipase C with the exception of phosphatidylserine and phosphatidylinositol. In intact microsomes about 90% of phosphatidylcholine, 32% of ethanolamine phospholipids and 60% of sphingomyelin were accessible to the phospholipase. These results suggest that the phospholipids have an asymmetric distribution in chicken brain microsomes, the external leaflet containing about 75% of the choline phospholipids and 25% of the aminophospholipids, whereas an opposite distribution is observed in the inner leaflet.