CHARACTERIZATION OF MICROVILLAR MEMBRANE-PROTEINS OF DOG SMALL-INTESTINE BY 2-DIMENSIONAL ELECTROPHORESIS

A method for analysing microgram amounts of microvillar membranes by t wo-dimensional electrophoresis (protein mapping) is described, and has been used to characterize the microvillar proteins of the small intes tine of German shepherd, corgi, and beagle dogs. Detergent-solubilized microvillar membranes were radiolabelled with C-14 and separated by i soelectric focussing followed by SDS-PAGE, Proteins were detected fluo rographically and glycoproteins by lectin-affinity staining, The micro villar hydrolases alkaline phosphatase and dipeptidyl aminopeptidase I V were identified by active-site labelling and aminopeptidase N by imm unoprecipitation. Changes following pancreatic duct diversion were con sistent with accumulation of pro-sucrase-isomaltase and diminished exp ression of the sucrase and isomaltase subunits. Cytoskeletal proteins were concentrated in the core fraction remaining after extraction of m icrovillar membranes with Triton X-100. There were no consistent diffe rences between dogs of different breed, and the canine protein maps we re similar to the human.