Research from Austria has unveiled the ‘lock-and-key’ mechanism of human fertilisation, using studies in zebrafish, mice, and human cells.

It was known that sperm cells had the ‘key’ to ‘unlock’ the egg, by binding to a receptor on the surface of the egg, beginning the process of fertilisation, but the way that mechanism worked was unknown.

Researchers from the Research Institute of Molecular Pathology (IMP), Vienna, used Google DeepMind’s artificial intelligence tool AlphaFold — whose developers were awarded the Nobel Prize for Chemistry earlier this month — to help them identify a new complex in sperm cells composed of three proteins.

Two were already known to contribute to fertilisation, while the other, whose function was previously unknown, was found to be the crucial molecular connection between sperm and egg.

Although the egg receptor is different in fish and in mammals, the AI also predicted that the complex would bind to both types of receptor. The researchers then tested this in zebrafish, and both mice and human cells and found the prediction to be accurate.

Andrea Pauli, lead researcher at IMP, said: “The fact that [the sperm complex] was maintained over millions of years of evolution shows just how important this lock-and-key process is.”

The study was recently published in Cell.