title: Determination of the absolute number of Escherichia coli membrane vesicles that catalyze active transport.
abstract: Transport of vinylglycolate (2-hydroxy-3-butenoic acid) via the lactate transport system is the limiting step for covalent labeling of membrane vesicles prepared from E. coli ML 308-225. Thus, the rate and extent of vinylglycolate labeling is stimulated about 10-fold by ascorbate-phenazine methosulfate, and stimulation is abolished by 2,4-dinitrophenol and by phospholipase treatment, neither of which affect the rate of vinylglycolate oxidation. [(3)H]Vinylglycolate of high specific activity has been prepared, and vesicles have been labeled with this compound in the presence of ascorbate-phenazine methosulfate. Examination of these preparations by high resolution radioautography in the electron microscope demonstrates that virtually all of the vesicles are labeled. The experiments provide a strong indication that most, if not all, of the membrane vesicles in these preparations catalyze active transport.
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D001345:Autoradiography; D001693:Biological Transport, Active / Q000187:drug effects; D002384:Catalysis; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D004140:Dinitrophenols / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism / Q000648:ultrastructure*; D005947:Glucose / Q000378:metabolism; D006880:Hydroxy Acids / Q000378:metabolism*; D008854:Microscopy, Electron; D010619:Phenazines / Q000494:pharmacology; D010728:Phosphoenolpyruvate; D010770:Phosphotransferases / Q000378:metabolism; D014316:Tritium; D014753:Vinyl Compounds / Q000378:metabolism
chemical_list: D004140:Dinitrophenols; D006880:Hydroxy Acids; D010619:Phenazines; D014753:Vinyl Compounds; D014316:Tritium; D010728:Phosphoenolpyruvate; D010770:Phosphotransferases; D005947:Glucose; D001205:Ascorbic Acid