Fine-scale structure of egg crucial for fertility
The shape of a protein that forms a key coating on an egg provides an atomic view of conception
If fertility had a shape, this would be it.
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Scientists have figured out the exact shape of part of a protein that sits on the outside of the egg and aids in fertilization. The results, which may ultimately lead to new contraceptives and treatments for infertility, appear in the Dec. 4 Nature.
On its quest to fertilize an egg, a sperm cell must first get through the outer layer of the egg. Proteins composing this outer layer — called the zona pellucida — have two major jobs during fertilization. The first is to recognize that a sperm cell is from the correct species, and the second is to tighten into a solid shell that seals off the egg as soon as the first lucky sperm penetrates. This barrier prevents other sperm from fertilizing the egg, an event that would be lethal.