A 70-KDA PROTEIN IS TRANSFERRED FROM THE OUTER ACROSOMAL TO THE PLASMA-MEMBRANE DURING CAPACITATION

Bull sperm plasma and outer acrosomal membranes were analyzed by SDS-P AGE, Analysis of the plasma membrane proteins revealed the presence of a 70 kDa band the prominence of which is enhanced after capacitation, This protein was found to bind to zona pellucida intact oocytes, PAGE analysis of outer acrosomal membrane proteins also reveals the presen ce of a 70 kDa band, but its prominence decreases after capacitation. This protein also binds to zona pellucida intact oocytes, Futhermore, the 70 kDa outer acrosomal membrane protein is recognized in Western b lot analysis by antibodies to plasma membrane proteins and vice versa, The results indicate that the 70 kDa acrosomal and plasma membrane pr oteins are the same, This 70 kDa protein would thus be a zona pellucid a binding protein which is initially stored in the outer acrosomal mem brane and transferred to the plasma membrane during capacitation, enab ling it to function in egg-sperm binding.