An unexpected new element was discovered by researchers from Sweden in the structure of spermatozoa. As it turned out, the flagellum of male germ cells contains previously unexplored protein structures. They are twisted in the form of a spiral and are located in the cavity of microtubules.
The uniqueness of this discovery lies in the fact that the researchers found these spirals in a single place in all spermatozoa that were examined under a microscope. They are located at the very tip of the tail (flagellum). According to scientists, further research in this area can make a breakthrough in the treatment of male infertility.
The discovery of the Swedes is mentioned in a material published in the scientific publication Scientific Reports. The structures located in the cavity of microtubules were revealed in the process of studying the spermatozoon using cryoelectron tomography.
The essence of this method is that the object of study is subjected to instant freezing, after which the biomaterial is translucent using an electron microscope. Next, the obtained images are combined into a single three-dimensional model.
After studying the model obtained as a result of cryoelectron tomography of the sperm, the researchers identified spirals at the tip of the flagellum. Previously, it was known that the tail of the male germ cell itself consists of a series of hollow microtubules, to which special “motor” proteins are attached. It is with their help that the spermatozoon moves. Now it turned out that in the cavity of microtubules at the very tip of the flagellum there are protein spirals, which researchers have already compared with “corks in a bottle.”
So far, scientists cannot unequivocally determine the purpose of this element. According to one theory, they are designed to control how microtubules interact with motor proteins. In particular, scientists suggest that spirals are able to prevent the process of expansion or contraction of the tubes. The second version says that the spirals play the role of a kind of “video recorder”, which helps the sperm to bypass the obstacles that arise in its path and assists in finding the egg.