The topology of sialoglycoconjugates (SGCs) and mannose/glucose glycocomponents (M/GCs) was studied in two plasma membrane domains of polarized cells. SGCs and M/GCs were localized in situ, by WGA and Con A labeling respectively, in four membrane planes: external and cytoplasmic surfaces; exoplasmic and endoplasmic faces of freeze-dissected membranes. SGCs and M/GCs are asymmetrically inserted in the plasma membrane, being preferentially associated with outer membrane halves of the studied cells; correlation between SGCs and membrane-intercalated particles densities is observed in protoplasmic halves of the membrane domains, thus suggesting that membrane domains (defined by surface probes) may be conditioned by integral membrane components; 'fracture-label' allows the detection of SGCs and M/GCs expressed at the external surface that are masked by the cell coat and are not accessible to surface probes in intact cells.
NIH ExPorter
NIH ExPorter