bims-tricox Biomed News
on Translation, ribosomes and COX
Issue of 2022–12–18
two papers selected by
Yash Verma, University of Delhi South Campus
  1. A male germ-cell-specific ribosome controls male fertility.
  2. On the Mechanism of Sustained Mitochondrial Membrane Potential Without Functioning Complex IV.
  1. Nature. 2022 Dec 14.
    A male germ-cell-specific ribosome controls male fertility.
    Huiling Li, Yangao Huo, Xi He, Liping Yao, Hao Zhang, Yiqiang Cui, Huijuan Xiao, Wenxiu Xie, Dejiu Zhang, Yue Wang, Shu Zhang, Haixia Tu, Yiwei Cheng, Yueshuai Guo, Xintao Cao, Yunfei Zhu, Tao Jiang, Xuejiang Guo, Yan Qin, Jiahao Sha.
      Ribosomes are highly sophisticated translation machines that have been demonstrated to be heterogeneous in the regulation of protein synthesis1,2. Male germ cell development involves complex translational regulation during sperm formation3. 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.
    DOI:  https://doi.org/10.1038/s41586-022-05508-0
  2. Adv Exp Med Biol. 2022 ;1395 367-372
    On the Mechanism of Sustained Mitochondrial Membrane Potential Without Functioning Complex IV.
    Eiji Takahashi, Yoshihisa Yamaoka.
      In intact mitochondria, the transport of electrons, respiration and generation of proton gradients across the inner membrane (proton motive force) are mutually coupled, according to Peter Mitchell's hypothesis on oxidative phosphorylation. Thus, the inhibition of electron transport at either respiratory complex III or IV in the electron transport chain leads to failure in producing proton motive force along with the abolition of respiration. Here, we determined the mitochondrial membrane potential (MMP), as a measure of proton motive force, and cellular respiration in various cultured cells and demonstrated that inhibition of complex IV by KCN abolished mitochondrial respiration while MMP was sustained. These results are unexpected and appear incompatible with Mitchell's chemiosmotic hypothesis.
    Keywords:  Electron transport; Mitchell’s chemiosmotic hypothesis; Mitochondria; Proton motive force
    DOI:  https://doi.org/10.1007/978-3-031-14190-4_60
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