Egg lysin creates a hole in the envelope of the egg thereby allowing the sperm to pass through the envelope and fuse with the egg.

1: The crystal structure of lysin, a fertilization protein. Shaw A, McRee DE, Vacquier VD, Stout CD; Science 1993;262:1864-1867. PMID:8266073

2: Crystal structure and subunit dynamics of the abalone sperm lysin dimer: egg envelopes dissociate dimers, the monomer is the active species. Shaw A, Fortes PA, Stout CD, Vacquier VD; J Cell Biol 1995;130:1117-1125. PMID:7657696