Distribution of Saccharide Residues on Membrane Fragments from a Myeloma-Cell Homogenate: Its Implications for Membrane Biogenesis

Distribution of Saccharide Residues on Membrane Fragments from a Myeloma-Cell Homogenate: Its Implications for Membrane Biogenesis

^*Department of Biology, University of California at San Diego, La Jolla, Calif. 92037
^‡Armand Hammer Center for Cancer Biology, The Salk Institute for Biological Studies, San Diego, California 92112

Abstract

Ferritin conjugates of two plant agglutinins, concanavalin A and ricin, have been used as specific electron microscopic stains for covalently-bound saccharide residues on membrane fragments from a myeloma-cell homogenate. The results indicate that different saccharide residues are uniformly localized to a single surface of each membrane fragment. In particular, the ferritin-concanavalin A conjugate binds exclusively to the cisternal side of membrane fragments of the rough endoplasmic reticulum. If it is postulated that the biogenesis of eukaryotic plasma membranes involves an assembly-line process from precursor intracellular membranes, these observed asymmetric distributions of saccharides on cell membranes can be explained.

Footnotes

↵ † Present address: Department of Anatomy, Kyorin University Medical School, Shinkawa Mitaka, Tokyo, Japan.
↵ § Present address: Department of Molecular Biology, University of California at Berkeley, Berkeley, Calif. 94720.
↵ ¶ To whom reprint requests should be addressed.