Isolation of yeast plasma membranes.

The plasma membrane is dynamic, with both its lipid and protein composition changing to facilitate adaptation to the ambient conditions. Biochemical activities to pre-existing proteins will also change. To monitor these variations, the cell membrane must be isolated. Moreover, the preparations must be free of contamination from the variety of other membranes in the cell, principally those associated with the golgi, endoplasmic reticulum (ER), the nucleus, and the vacuole. We describe a method for isolating plasma membranes that avoids incubation with enzymes that degrade the cell wall, thereby avoiding physiological changes that may lead to alteration in profile and activity of membrane proteins as well as avoiding changes that may alter lipid composition. We have used this method to show that, in response to heat shock, the plasma membrane acquires a novel heat-shock protein (HSP) and displays a decline in the levels of the abundant H+ translocating ATPase.