Could be useful both for fertility and contraception:

A fundamental key to fertility has been uncovered by British scientists with the discovery of an elusive protein that allows eggs and sperm to join together.

The molecule – named Juno after the Roman goddess of fertility – sits on the egg surface and binds with a male partner on a fertilising sperm cell.

Japanese researchers identified the sperm protein in 2005, sparking a decade-long hunt for its "mate".

Understanding the process by which the molecules interact opens the door to new developments in fertility treatment and contraception.