Composition and properties of a cell-membrane fraction from the polymorphonuclear leucocyte.

1. The composition of a vesicular cell-membrane fraction from leucocytes has been studied. The bulk of the mass is accounted for as protein and lipid. A small amount of carbohydrate, including some N-acetylneuraminic acid, is present. The phospholipid/cholesterol molar ratio is 1.4 and differs from that for the whole cell. 2. Labile phosphorus groups are present in the membrane but the analysis is complicated by the presence of phosphorus occluded in the membrane vesicles. 3. Leucocidin does not change the gross composition of the membranes or alter the amount or reactivity of the phosphorus compounds. 4. The cell-membrane fraction has considerable avidity for an impurity present in commercial [(32)P]orthophosphate. When this is removed [(32)P]orthophosphate or [(32)P]ATP does not label the membrane. 5. The presence of an NADH(2)-cytochrome c oxidoreductase and an alkaline phosphatase is described. The adenosine-triphosphatase activity of the membrane has not been found to depend on the presence of Na(+) or K(+).