Figure 1.

The chymotrypsin-like activity of the sperm proteasome increases at the onset of human sperm capacitation. Spermatozoa were incubated under capacitating conditions for the indicated time periods. The chymotrypsin-like activity of the sperm proteasome was evaluated using the fluorogenic substrate N-succinyl-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin (Suc-LLVY-AMC). An additional sperm aliquot was incubated under capacitating conditions for 60 min in the presence of 10 μM epoxomicin (60 + Epox). Data are expressed as mean ± SEM of five experiments. ^**P < 0.01; ^***P < 0.001 compared to time 0. In the insert, the upper panel represents the abundance of the PSMA7 subunit of the sperm proteasome at each capacitation time; the lower panel corresponds to the load control evaluated with an anti ß-tubulin antibody.