Figure 1.

Protein-tyrosine phosphorylation and the biology of sperm. A sequence of events in the sperm must be done to facilitate a successful fertilization. The events include spermatogenesis and epididymal maturation that occur in the male reproductive organs, capacitation/hyperactivation and acrosomal exocytosis (or acrosome reaction, AE) in the female reproductive tract (in the case of species employing internal fertilization: e.g., mammals) or in the extracellular space (in the case of species employing external fertilization: e.g., frogs and fishes), and gamete interaction and fusion at the plasma membranes. In all of these processes, protein-tyrosine phosphorylation catalyzed by SFKs (e.g., Src) and/or other PTKs (e.g., EGFR, Abl) is suggested to play an important role. For details, see text.