Human testis tissue lysate was prepared by homogenization in lysis buffer (10 mM HEPES, pH 7.9, 1.5 mM MgCl2, 10 mM KCI, 1 mM ethylenediaminetetraacetic acid, 10% glycerol, 1% NP-40, and a cocktail of protease inhibitors).

Tissue and cell debris was removed by centrifugation.
Protein concentration was determined with Bio-Rad protein assay.

The lysate was boiled for 5 min in 1 x SDS sample buffer (50 mM Tris-HCl, pH 6.8, 12.5% glycerol, 1% sodium dodecylsulfate, 0.01% bromophenol blue, 50 mM DTT