Biochemical studies of taste sensation. XI. Isolation, characterization and taste ligand binding activity of plasma membranes from catfish taste tissue.
Plasma membranes were isolated from taste receptor-containing epithelium of the channel catfish, Ictalurus punctatus. The membranes were prepared by ultracentrifugation of a sedimentable fraction in sucrose, using either a discontinuous density gradient or a continuous linear density gradient. The plasma membranes were characterized by their increased content of 5'-nucleotidase and by electron microscopy, as well as by a greatly diminished content of NADH-cytochrome c reductase and succinate-cytochrome c reductase. The recovery of binding activity for taste ligands was low, because of the long time-period required for ultracentrifugation, but of the recovered activity 80% occurred in the plasma-membrane preparation. Binding of seven chemostimulatory amino acids was demonstrated and found to correspond reasonably well with earlier binding data obtained using a less pure sedimentable fraction. The data provide direct evidence supporting the long-standing hypothesis that taste receptor sites are localized to the plasma membranes.
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D005399:Fishes / Q000502:physiology*; D008854:Microscopy, Electron; D009245:NADH Dehydrogenase / Q000378:metabolism; D013379:Substrate Specificity; D013649:Taste / Q000502:physiology*; D013650:Taste Buds / Q000166:cytology*; D014461:Ultracentrifugation
D000596:Amino Acids; D009245:NADH Dehydrogenase