Ovastacin cuts off sperm binding

Apr 02, 2012
A study in the Journal of Cell Biology describes how ovastacin helps egg cells avoid being fertilized by more than one sperm. In this image, ovastacin (red) localizes to secretory granules (green) in the cortex of an unfertilized egg. Credit: Burkart, A.D., et al. 2012. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201112094.

A study in The Journal of Cell Biology describes how a secreted enzyme helps egg cells avoid being fertilized by more than one sperm.

Because polyspermy disrupts , oocytes take several steps to ensure they only fuse with a single sperm. One key step is to prevent additional sperm from binding to the surface of an already-fertilized egg, a that involves the release of secretory granules and of a protein called ZP2, a component of the zona pellucida matrix that surrounds eggs. ZP2 is cleaved at a site targeted by the astacin family of metalloendoproteases – enzymes that cut proteins into smaller fragments. Researchers from the NIH's National Institute of Diabetes and Digestive and Kidney Diseases therefore investigated the function of ovastacin, an astacin family member expressed in oocytes.

Ovastacin localized to cortical granules that were exocytosed after fertilization, and recombinant ovastacin cleaved ZP2 when added to zonae pellucidae. Mice lacking ovastacin failed to cleave ZP2 after fertilization, allowing sperm to continue to bind to the surface of early embryos. Female mice lacking ovastacin had slightly fewer offspring than wild-type animals but otherwise appeared normal.

The researchers found that ovastacin targeted several sites in ZP2. Senior author Jurrien Dean now wants to investigate how this proteolysis blocks sperm binding, a critical question because the molecular interactions between sperm and remain unknown. He also wants to examine how ovastacin is packaged into oocyte cortical granules and to identify other components of these secretory organelles.

Explore further: Structure of an iron-transport protein revealed

More information: Burkart, A.D., et al. 2012. J. Cell Biol. dx.doi.org/10.1083/jcb.201112094

add to favorites email to friend print save as pdf

Related Stories

Egg meets sperm: The female side of the story

Oct 21, 2010

Researchers at the Swedish medical university Karolinska Institutet have been able to describe the 3D structure of a complete egg receptor that binds sperm at the beginning of fertilization. The results, published in the ...

New requirements for male fertility

Apr 26, 2010

Two independent groups of researchers have identified distinct roles for two proteins in a family of proteins known as PLA2s as crucial for sperm function and fertility in mice. These data identify proteins that could underlie ...

Making sperm from stem cells in a dish

Aug 04, 2011

Researchers have found a way to turn mouse embryonic stem cells into sperm. This finding, reported in the journal Cell in a special online release on August 4th, opens up new avenues for infertility research and treatment. A Kyo ...

Researchers Develop Test to Identify 'Best' Sperm

May 20, 2010

(PhysOrg.com) -- Researchers at Yale School of Medicine have discovered a method to select sperm with the highest DNA integrity in a bid to improve male fertility. The method is comparable to that of the egg’s ...

Recommended for you

Scientists see how plants optimize their repair

5 hours ago

Researchers led by a Washington State University biologist have found the optimal mechanism by which plants heal the botanical equivalent of a bad sunburn. Their work, published in the Proceedings of the Na ...

Structure of an iron-transport protein revealed

11 hours ago

For the first time, the three dimensional structure of the protein that is essential for iron import into cells, has been elucidated. Biochemists of the University of Zurich have paved the way towards a better ...

Over-organizing repair cells set the stage for fibrosis

12 hours ago

The excessive activity of repair cells in the early stages of tissue recovery sets the stage for fibrosis by priming the activation of an important growth factor, according to a study in The Journal of Ce ...

User comments : 0