31P nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. III. The outer membrane.
1. The outer membrane of a phospholipase A-deficient mutant of Escherichia coli K12, isolated without the use of EDTA and lysozyme, showed the same freeze-fracture morphology as that seen in cells and remained stable for hours as observed by 31P-NMR. 2. 31P-NMR spectroscopy of the isolated outer membranes revealed that the lipopolysaccharide exists in the same physical state as in phospholipid-lipopolysaccharide liposomes and is most probably arranged in a bilayer at 37 degrees C. The outer membrane contains most or all of the phospholipids at 37 degrees C, and all the phospholipids at 20 degrees C, as a bilayer. 3. The 31P-NMR spectroscopy of the outer membranes from a mutant strain lacking the major  outer membrane protein b, c and d (60% of the total outer membrane protein) yields virtually the same spectrum as the wild-type outer membranes, although most of the particles and pits which were observed in wild-type outer membranes in freeze-fracture electron microscopy were absent. 4. Whereas treatment of wild-type outer membranes with calcium ions has no effect on the 31P-NMR spectrum, treatment with EDTA results in more motion of the lipopolysaccharide.
D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism*; D005614:Freeze Fracturing; D008070:Lipopolysaccharides / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008854:Microscopy, Electron; D009154:Mutation; D010741:Phospholipases A / Q000235:genetics; D010743:Phospholipids / Q000378:metabolism*
D008070:Lipopolysaccharides; D010743:Phospholipids; D004492:Edetic Acid; D010741:Phospholipases A; D002118:Calcium