Similarity and limited multiplicity of membrane proteins from rough and smooth endoplasmic reticulum.

During electrophoresis on acrylamide gel 30 to 45 percent of the protein of hepatic microsomal membranes migrates as a single band corresponding to a molecular weight of 52,000. Rough and smooth microsomal membranes exhibit essentially identical electrophoretic patterns. Different findings by previous workers may be the result of contamination of the membranes by adsorbed and entrapped nonmembrane protein.