FIG. 4.

Analysis of the proteins extracted from MA104 cells. Cell monolayers were treated with either neuraminidase, tunicamycin, or PDMP, as described in Materials and Methods, and the cells were then extracted with 0.2% OG for 90 min at room temperature. (A) The extracted proteins were separated by electrophoresis under reducing conditions in an SDS–11% polyacrylamide gel and silver stained. OG-extracted proteins from MA104 cells treated with neuraminidase (lane 2), tunicamycin (lane 3), or PDMP (lane 4) or left untreated (lane 5) are shown. Lane 1 contains molecular mass markers. (B) Cells in suspension were extracted with 10 mM β-cyclodextrin for 1 h at 37°C, as described in Materials and Methods. Proteins in untreated cells (lane 1), extracted cells (lane 2), and the cyclodextrin extract (lane 3) were analyzed by gel electrophoresis.