Endocytosis in erythrocytes and ghosts: occurrence at 0 degrees C after ATP preincubation |
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Authors: | J T Penniston L Vaughan M Nakamura |
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Institution: | Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota 55901 USA |
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Abstract: | Two steps were required for ATP-dependent endocytosis in resealed erythrocyte ghosts. The first step required incubation with Mg-ATP at 37 °C, while the second step required primaquine and occurred at 0 or at 37 °C. These two steps were apparently also required for ATP-dependent endocytosis in erythrocytes. Endocytosis in white ghosts was similar to that in resealed ghosts and erythrocytes; the main difference was that the requirement of primaquine for the second step was less strict in white ghosts; in them, appreciable endocytosis took place with no added primaquine. Nonetheless, endocytosis in all three types of cells was stimulated by primaquine. The fluidity of the membranes as sensed by spin-labeled phosphatidylcholine was measured with and without primaquine. The fluidity of erythrocytes was increased by addition of primaquine or by conversion of the erythrocytes to white ghosts; the effect primaquine had on the fluidity of white ghosts was not detectable by the spin label. This suggested that a fluidizing or loosening of the membrane structure was required for the second step of ATP-dependent endocytosis, and that this loosening could be accomplished either by primaquine or by the process of preparing white ghosts. |
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Keywords: | To whom correspondence should be addressed |
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