Researchers have found on "interacting protein" on the surface of both the sperm and egg that help bring about mammalian life. 

The protein help the sperm and egg recognize each other; this finding could help lead to new fertility therapies, a Wellcome Trust Sanger Institute news release reported. 

"We have solved a long-standing mystery in biology by identifying the molecules displayed on all sperm and egg that must bind each other at the moment we were conceived," Doctor Gavin Wright, senior author from the Sanger Institute, said in the news release. "Without this essential interaction, [fertilization] just cannot happen. We may be able to use this discovery to improve fertility treatments and develop new contraceptives."

The protein was named Izumo after a Japanese marriage shrine. Izumo pairs with another protein named Juno, after Roman goddess of fertility. 

"We have solved a long-standing mystery in biology by identifying the molecules displayed on all sperm and egg that must bind each other at the moment we were conceived," Doctor Gavin Wright, senior author from the Sanger Institute. "Without this essential interaction, fertilisation just cannot happen. We may be able to use this discovery to improve fertility treatments and develop new contraceptives."

Researchers created an artificial Izumo protein in order to identify its binding partners on the egg's surface. The team found the protein interacted with Juno in this situation. 

The researchers developed mice that lacked the Juno protein; these mice proved to be infertil because their proteins could not bind with regular sperm. 

"The Izumo-Juno pairing is the first known essential interaction for sperm-egg recognition in any organism," Doctor Enrica Bianchi, first author from the Wellcome Trust Sanger Institute, said in the news release. "The binding of the two proteins is very weak, which probably explains why this has remained a mystery until now."

"Previous work in the laboratory led us to expect the interaction to be weak, and this then guided the design of our experiments, and, after a lot of effort, it finally worked," Bianchi said.