The successful union of egg and sperm in fertilisation depends on a sperm cell's ability to get through an egg's thick protective coating and latch itself to its membrane. A study published in the journal Andrology yesterday gives us our first look at the protein responsible for the tie-down.
Sperm-lysozyme-like protein 1 (SLLP1, above) is found inside a part of the sperm's head called the acrosome, a region that was already known to host enzymes that help a sperm drill through an egg's gelatinous coating.
University of Virginia researchers from the labs of John Herr and Wladek Minor have determined that SLLP1 looks something like the prong of a mutant USB cord: a group of six smaller proteins wrapped in a helix around a central space. The filaments plug into a protein called ovastacin that is only found near the surface of the egg. Ovastacin also plays a role in preventing multiple sperm from entering the egg, suggesting that these two proteins play a key role in sparking the process of fertilisation.
Picture: Heping Zheng, Ph.D., University of Virginia School of Medicine