Characterization of brush borders purified in iso-osmotic medium and microvillar membranes subfractionated from mouse small intestine.
Brush borders free of nuclei were isolated by repeated homogenization and centrifugation in iso-osmotic medium. They showed typical morphology under electron microscopy. The mean recovery and enrichment of alkaline phosphatase activity in the brush-border fraction were 50% and 17.5-fold respectively. gamma-Glutamyl transpeptidase showed a close parallelism with alkaline phosphatase and sucrase in subcellular distribution. Microvillar membranes were purified from isolated brush borders; they showed a further enrichment for alkaline phosphatase and were composed of homogeneous vesicles. Both brush-border and microvillar-membrane preparations were analysed for contamination by basolateral and endoplasmic-reticular membranes. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of the microvillar-membrane preparation in six different systems revealed approx. 40 components in the mol.wt. range 15 000-232 000. They were grouped into seven major classes on the basis of molecular weight and electrophoretic patterns.
D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007425:Intracellular Membranes / Q000201:enzymology / Q000648:ultrastructure; D007583:Jejunum / Q000201:enzymology / Q000648:ultrastructure*; D008297:Male; D051379:Mice; D008871:Microvilli / Q000201:enzymology / Q000648:ultrastructure