Description:
<jats:p>Phospholipase C treatment of <jats:italic>Bacillus megaterium</jats:italic> protoplasts at 37°C removed up to 63% of the total phospholipid without disrupting the membrane. More than 95% of the total phosphatidylethanolamine and 3′‐glucosaminylphosphatidylglycerol, 80% of the phosphatidylglycerol and about 20% of the cardiolipin and 2′‐glucosaminylphosphatidylglycerol were hydrolyzed.</jats:p><jats:p>Similar results were obtained with isolated membranes and dispersions of lipids extracted from the membranes, demonstrating that these data do reflect, at least in part, the substrate specificity of phospholipase C and not necessarily the distribution of phospholipids over the two membrane layers.</jats:p><jats:p>When protoplasts and isolated membranes were incubated with excess phospholipase C at temperatures in between 5°C and 25°C a different hydrolysis pattern was obtained and it was concluded that 50% of the phosphatidylethanolamine and 70% of the 3′‐glucosaminylphosphatidylglycerol are located in the outer membrane layer, the residual being in the cytoplasmic layer. At least 40% of the phosphatidylglycerol was found to be present also in the outer layer. The data do not allow conclusions about the localization of cardiolipin and 2′‐glucosaminylphosphatidylglycero1. Trinitroben‐zenesulfonic acid reacted with 50% of the phosphatidylethanolamine in protoplasts and with nearly 100% of this lipid in isolated membranes at various temperatures and concentrations, thus confirming the symmetric localization of this lipid.</jats:p><jats:p>The data furthermore indicate that a temperature‐dependent transbilayer movement of phospholipids is induced by phospholipase C treatment of the <jats:italic>Bacillus megaterium</jats:italic> protoplasts.</jats:p>