Newly discovered Specialized Sperm Ribosomes Are Key to Male Fertility in Mice

Amazing stuff! It confirms that specialized ribosomes exist and that they are essential. There is some potential for future male contraceptives or to explain some forms of male infertility.

"A newly discovered type of ribosome, which synthesizes and then neatly and securely folds the proteins in sperm to prepare them for their arduous journey, seems to play a key role in male reproductive health ...
the ribosome packages proteins in a special way that enables them to last long enough to achieve fertilization. ...

that RibosomeST possesses a structurally distinct exit tunnel through which newly formed polypeptide chains pass and begin to fold into their final shape. ...
Further experiments on mouse cell lines showed that RibosomeST is the only ribosome capable of properly folding proteins essential to spermatogenesis ...
It provides a serious piece of heft to the hypothesis that specialized ribosomes not only exist but have important functional consequences in cellular processes. ..."

From the abstract:

"Ribosomes are highly sophisticated translation machines that have been demonstrated to be heterogeneous in the regulation of protein synthesis. Male germ cell development involves complex translational regulation during sperm formation. However, it remains unclear whether translation during sperm formation is performed by a specific ribosome. Here we report a ribosome with a specialized nascent polypeptide exit tunnel, RibosomeST, that is assembled with the male germ-cell-specific protein RPL39L, the paralogue of core ribosome (RibosomeCore) protein RPL39. Deletion of RibosomeST in mice causes defective sperm formation, resulting in substantially reduced fertility. Our comparison of single-particle cryo-electron microscopy structures of ribosomes from mouse kidneys and testes indicates that RibosomeST features a ribosomal polypeptide exit tunnel of distinct size and charge states compared with RibosomeCore. RibosomeST predominantly cotranslationally regulates the folding of a subset of male germ-cell-specific proteins that are essential for the formation of sperm. Moreover, we found that specialized functions of RibosomeST were not replaceable by RibosomeCore. Taken together, identification of this sperm-specific ribosome should greatly expand our understanding of ribosome function and tissue-specific regulation of protein expression pattern in mammals."

Specialized Sperm Ribosomes Are Key to Male Fertility in Mice | The Scientist Magazine® A previously unknown kind of ribosome is responsible for folding sperm proteins, which decay before fertilization if prepared by other ribosomes.

A male germ-cell-specific ribosome controls male fertility (no public access, but the article above contains a link to the PDF file)