Preparation of protein extracts from yeast

Three protocols are presented for preparing protein extracts; they differ primarily in the way the cells are broken. In the basic protocol, cells are enzymatically converted to spheroplasts, which are then lysed by a combination of osmotic shock and Dounce homogenization. A support protocol for isolating intact nuclei by differential centrifugation is also presented. An alternate protocol describes mechanical breakage of cells by vortexing in the presence of glass beads. In a second alternate protocol, growing cells are frozen immediately in liquid nitrogen and then lysed by grinding in an industrial-strength blender in the presence of liquid nitrogen.