Researchers from the University of Virginia have discovered a protein that acts like a tiny harpoon to allow the sperm to attach itself to the egg and fertilize it.
It took the team almost 14 years to identify this protein which resides in the head of the sperm and forms spiky filaments using which it later latches onto the egg.
Lead author John Herr, reproduction researcher of the Department of Cell Biology, “This finding has really captured our imagination.”
“One of the major proteins that is abundant in the acrosome [in the anterior region of the sperm head] is crystallizing into filaments, and we now postulate they’re involved in penetrating the egg – that’s the new hypothesis emerging from the finding, which leads to a whole new set of questions and new hypotheses about the very fine structure of molecular events during fertilisation,” Herr said.
The researchers were able to come to this conclusion after Herr’s lad joined hands with another lab, Wladek Minor from the Department of Molecular Physiology and Biological Physics in a bid to understand the process of fertilisation.
Years ago, Herr had discovered SLLP1, a protein which eases fertilisation, but was unable to gain a deeper insight into HOW the said protein did so.
Mindor and his colleagues captured the protien within a static crystal to understand its structure. The captured protein was later chilled for protection and X-rayed to know more about its shape.
“This is an important protein, because it’s the first crystal structure from a protein within the sperm acrosome,” said Heping Zheng, the lead author of the discovery.
“It is also the first structure of a mammalian sperm protein with a specific oocyte-side binding partner characterized. To our knowledge, only nine proteins specifically obtained from mammalian sperm have known structures,” Zheng said.
The new understanding will now help reproductive biologists understand the process of fertilization more accurately.
The findings were published in the journal Andrology.