Yeast cells were disrupted using zirconium-silica beads (0.45-0.5 mm).

Lysis buffer:
50 mM Tris/HCl pH7.5
1 mM EDTA
0.5 % Triton X-100
1 mM DTT
1 M NaCl
1 x Complete Mini, pH7
2.5 µg/ml pepstatin 

BREAKAGE OF THE CELL WALL:

1.Cell pellets were defrosted on ice (2 x 1 ml samples, equivalent to
  50ml yeast culture expressing the protein of choice).

2.To each tube add zirconium-silica beads (0.45-0.5 mm) in a 1:1 (v/v)
  ratio to the cell pellet and 0.5 ml lysis buffer. The contents of
  the 2 tubes were combined in one 1-ml tube.

3.The tube contents were vigorously vortex-mixed for 30 s and cooled
  on ice for 30 s (repeated 10 times) to break open the cells to
  produce the cell lysate.

4.The lysate solution was left on ice and employed immediately for
  protein purification.