Yeast membrane vesicles: isolation and general characteristics.

Yeast membrane vesicles are formed when packed yeast are ground manually in a porcelain mortar and pestle with glass beads (0.2 mm diameter). These vesicles can be separated from the other components of the grinding mixture by a combination of centrifugation steps and elution from a column of the same glass beads (0.2 mm diameter). Isolated vesicles are osmotically sensitive, contain cytoplasmic components, and have energy-independent transport function. They are unable to metabolize glucose, but have respiratory function which is thought to be associated with intravesicular mitochondria. Invertase and oligomycin-insensitive adenosine triphosphatase are present in lysed vesicle preparations, and the appropriateness of these enzyme activities as membrane markers is discussed.