A switch was identified by scientists, which triggers the ‘power kick’ sperms use for the fertilization of human egg. This could uncover a probable source of male infertility as well as a target for  unisex contraceptives.

The switch is a protein receptor that reacts to progesterone. Progesterone is a female sex hormone released by the oocyte or egg. The ultimate goal of the sperm is the oocyte and thus swims towards it. The tail surface of the sperm has thousands of receptors. When the sperm gets closer to the egg, the receptor gets activated by the hormone, triggering a cascade of changes. Thus, the tail snaps like a whip and powers the sperm into and through the cells, which protect the egg.

University of California, Berkeley, postdoctoral fellow, Melissa Miller said,"If the receptor protein doesn't recognize progesterone, you would be infertile. This gives us an understanding of another pathway that is involved in human sperm activity."

A drug which can inactivate the newly discovered receptor could be a good ‘unisex’ contraceptive. Thus, either of the sexual partners can use.  

UC Berkeley assistant professor Polina Lishko said, "Now that we know the players, the next step is to look in other tissues that express these proteins to see whether progesterone acts on them in a similar manner to affect pain threshold adjustment in pain sensing neurons, surfactant production in the lungs or the excessive smooth muscle contractions found in asthma."

- Sumana