Purification of microvillus membrane vesicles from pig small intestine by immunoadsorbent chromatography

Microvillus membrane vesicles from pig small intestine, isolated by hypotonic lysis, Mg2+ aggregation of contaminants and differential centrifugation, have been further purified by immunoadsorbent chromatography. The vesicles adhere to an immunoadsorbent prepared by coupling antibodies raised against three of the principal proteins of the brush border membrane (aminopeptidase, sucrase-isomaltase and lactase) to Sepharose 4B. After the contaminants are removed by washing, the adherent vesicles are released from the immunoabsorbent by applying shear forces. The purity of the immunoadsorbed vesicles has been established by electron microscopy and by measuring the activity of marker enzymes. The enrichment factor is 1.17 +/- 0.02 for aminopeptidase and 0.70 +/- 0.05 for 5'-nucleotidase. The contamination of the preparation before immunoadsorption constitutes 10% of the membrane protein and consists mainly of basolateral membrane fragments as judged from marker enzyme determinations and the lipid composition.