Topography of the Dictyostelium discoideum plasma membrane: analysis of membrane asymmetry and intermolecular disulfide bonds.
Through the application of a unique method for isolating plasma membranes, it was possible to specifically iodinate cytoplasm-exposed plasma membrane proteins in vegetative cells of the cellular slime mold Dictyostelium discoideum. The original procedure [Chaney, L. K., & Jacobson, B. S. (1983) J. Biol. Chem. 258, 10062] which involved coating cells with colloidal silica has been modified to yield a more pure preparation. The presence of the continuous and dense silica pellicle on the outside surface of the isolated plasma membrane permitted the specific labeling of cytoplasm-exposed membrane proteins. Lactoperoxidase-catalyzed iodination was employed to label cell-surface and cytoplasm-exposed membrane proteins. The isolated and radioiodinated membranes were then compared and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The cell-surface and cytoplasmic face labeling patterns were distinct. A total of 65 proteins were found to be accessible to at least one surface of the membrane. Sixteen intermolecular disulfide bond complexes were observed in the plasma membrane of Dictyostelium; most of these complexes involved glycoproteins and, hence, were exposed to the cell surface.
Shiozawa
J A
JA
Department of Biochemistry, University of Massachusetts, Amherst 01003.
Jelenska
M M
MM
Jacobson
B S
BS
D002458:Cell Fractionation; D002462:Cell Membrane / Q000032:analysis* / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D004023:Dictyostelium / Q000032:analysis* / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D008565:Membrane Proteins / Q000032:analysis*; D008970:Molecular Weight
D008565:Membrane Proteins