Extracellular localization of proteasomes in human sperm.

The proteasome, a multienzymatic protease complex is present in human sperm. Here we present evidence indicating that the proteasome has an extracellular localization, on the plasma membrane of the sperm head. Motile sperm (>90%) in PBS were incubated with the proteasome inhibitors clasto-lactacystin beta-lactone or epoxomicin.