The proteins were collected by centrifugation at 10,000g for 10 min at 4 C,and the resulting pellet was dissolved in 100 lL of SDS sample buffer(0.0625 M Tris–HCl pH 6.8, 10% (v/v) glycerol, 5% (w/v) SDS,0.004% (w/v) bromophenol blue and 5% (v/v) 2-mercaptoethanol)(Laemmli, 1970).