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

June 15, 2017, Karolinska Institutet
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

Researchers identify blood biomarkers that may help diagnose, confirm concussions

April 20, 2018
Researchers from the University of California, Irvine, Georgetown University and the University of Rochester have found that specific small molecules in blood plasma may be useful in determining whether someone has sustained ...

DOR protein deficiency favors the development of obesity

April 20, 2018
Obesity is a world health problem. Excessive accumulation of fat tissue (adipose tissue) increases the risk of cardiovascular disease, hypertension, diabetes and some types of cancer. However, some obese individuals are less ...

Stem-cell technology aids 3-D printed cartilage repair

April 20, 2018
Novel stem-cell technology developed at Swinburne will be used to grow the massive number of stem cells required for a new hand-held 3-D printer that will enable surgeons to create patient-specific bone and cartilage.

Defect in debilitating neurodegenerative disease reversed in mouse nerves

April 19, 2018
Scientists have developed a new drug compound that shows promise as a future treatment for Charcot-Marie-Tooth disease, an inherited, often painful neurodegenerative condition that affects nerves in the hands, arms, feet ...

Enduring cold temperatures alters fat cell epigenetics

April 19, 2018
A new study in fat cells has revealed a molecular mechanism that controls how lifestyle choices and the external environment affect gene expression. This mechanism includes potential targets for next-generation drug discovery ...

Molecule that dilates blood vessels hints at new way to treat heart disease

April 19, 2018
Americans die of heart or cardiovascular disease at an alarming rate. In fact, heart attacks, strokes and related diseases will kill an estimated 610,000 Americans this year alone. Some medications help, but to better tackle ...

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.