Cell surface proteins extracted with urea from AH-66 hepatoma ascites cells

The cell surface structure of AH-66 hepatoma ascites cells was examined by extracting the intact AH-66 cells with urea and analyzing the extracted proteins. When AH-66 cells were suspended in 1 M urea, material composed of approximately 90% protein and 10% carbohydrate was released. The extracted proteins amounted to about 3% of the total cell proteins and were composed of approximately 30 species as analyzed by sodium dodecyl sulfate gel electrophoresis. The major bands had apparent molecular weights of 84,000 and 50,000--60,000 on the gel. In marked contrast to chick embryo fibroblasts, the extracted proteins contained no components stainable with periodic acid-Schiff reagent. Lactoperoxidase-catalyzed iodination of intact AH-66 cells showed that most of the urea-extractable proteins were located on the outer surface of the plasma membranes of AH-66 cells. It was also found that there are two integral proteins exposed on the outer surface of the plasma membranes of AH-66 cells; one is a major glycoprotein (with a molecular weight of 165,000) and the other is a periodate-Schiff-negative protein with a molecular weight of 130,000.