3-D images show how sperm binds to the egg surface

June 15, 2017
Human sperm stained for semen quality testing in the clinical laboratory. Credit: Bobjgalindo/Wikipedia

Researchers at Karolinska Institutet in Sweden have obtained the first 3D snapshots of a sperm protein attached to a complementary egg coat protein at the beginning of fertilisation. The study, which reveals a common egg protein architecture that is involved in the interaction with sperm in both mollusc and mammal, is published in the respected scientific journal Cell.

By transmitting the genetic information to the next generation and marking the beginning of a new life, the encounter between female and male gametes at fertilisation is one of the most fundamental processes in biology. Although egg and were first observed centuries ago, how sperm recognises the coat of the egg and penetrates it has remained unknown.

Using X-ray crystallographic data collected at the European Synchrotron Radiation Facility (ESRF), Luca Jovine's research team at Karolinska Institutet first visualised the sperm-interacting regions of two egg coat proteins, ZP2 in mammals (including humans) and VERL in the marine mollusc abalone (a classic model system of invertebrate fertilisation). Both of these molecules contain repeated sequences that play a key role in gamete recognition.

"Mammals and molluscs are thought to be separated by 600 million years of evolution, and their sperm receptor proteins are almost completely different in sequence. However, comparison of the structures conclusively demonstrates that ZP2 and VERL repeats share a common 3D architecture", says Luca Jovine, Professor of Structural Biology at the Department of Biosciences and Nutrition and the Center for Innovative Medicine at Karolinska Institutet.

Subsequently, the research group determined crystal structures of different VERL repeats bound to lysin, the counterpart of VERL on abalone sperm. This gave an unprecedented view of how gametes recognise each other in a species-specific way at the beginning of fertilisation.

"Abalone was our system of choice for this investigation, as it is one of the few organisms where cognate egg coat and sperm proteins are known. Moreover, different species of abalone spawn in the open sea but, despite overlapping habitats and breeding seasons, hybrids rarely occur", says Professor Jovine.

The VERL-lysin complex structures also suggest how lysin opens a hole into the egg coat, allowing sperm to penetrate into the egg.

"Gamete recognition was first compared to a lock and key mechanism more than one hundred years ago. Our study provides the first example of how this is achieved at the very beginning of ", concludes Luca Jovine.

Explore further: First vital step in fertilization between sperm and egg discovered

More information: Cell (2017). DOI: 10.1016/j.cell.2017.05.033

Related Stories

First vital step in fertilization between sperm and egg discovered

April 16, 2014
Researchers at the Wellcome Trust Sanger Institute have discovered interacting proteins on the surface of the sperm and the egg essential to begin mammalian life. These proteins, which allow the sperm and egg to recognize ...

Recommended for you

Want to win at sports? Take a cue from these mighty mice

July 20, 2017
As student athletes hit training fields this summer to gain the competitive edge, a new study shows how the experiences of a tiny mouse can put them on the path to winning.

'Smart' robot technology could give stroke rehab a boost

July 19, 2017
Scientists say they have developed a "smart" robotic harness that might make it easier for people to learn to walk again after a stroke or spinal cord injury.

Engineered liver tissue expands after transplant

July 19, 2017
Many diseases, including cirrhosis and hepatitis, can lead to liver failure. More than 17,000 Americans suffering from these diseases are now waiting for liver transplants, but significantly fewer livers are available.

Lunatic Fringe gene plays key role in the renewable brain

July 19, 2017
The discovery that the brain can generate new cells - about 700 new neurons each day - has triggered investigations to uncover how this process is regulated. Researchers at Baylor College of Medicine and Jan and Dan Duncan ...

New animal models for hepatitis C could pave the way for a vaccine

July 19, 2017
They say that an ounce of prevention is worth a pound of cure. In the case of hepatitis C—a disease that affects nearly 71 million people worldwide, causing cirrhosis and liver cancer if left untreated—it might be worth ...

Omega-3 fatty acids fight inflammation via cannabinoids

July 18, 2017
Chemical compounds called cannabinoids are found in marijuana and also are produced naturally in the body from omega-3 fatty acids. A well-known cannabinoid in marijuana, tetrahydrocannabinol, is responsible for some of its ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.