Associate Professor Yasushi Tamura (Prof. Toshiya Endo's group) and his co-researchers at Nagoya University have discovered that Tam41, a protein substance in the inner mitochondrial membrane, synthesizes cardiolipin, a phospholipid unique to mitochondria. Their paper was published online in Cell Metabolism on April 25, 2013.
The human body is composed of innumerable cells, and each cell possesses myriad membrane structures. Mitochondria are one of these structures, and produce biogenic energy, which is fundamental to good health. For proper mitochondrial functioning, it is necessary that mitochondrial membranes maintain the appropriate lipid composition. Also, when mitochondria change their quantity dynamically according to their environment (see figures), they must produce lipids accurately, as these lipids become the raw materials for mitochondria. In particular, cardiolipin, a lipid produced within mitochondria, is crucial to the functioning of mitochondria. However, the enzyme that produces cardiolipin had not previously been identified.
The group discovered that the synthetic enzyme of cardiolipin within mitochondria is Tam41, and that it is important in order for cells to propagate. On the other hand, they also found a protein which helps cells lacking Tam41 to proliferate, and thus made it clear that cells have a backup system that allows them to grow even without cardiolipin.Prof. Tamura and his co-researchers will continue to advance their research, and could contribute to the development of medical treatment for disorders caused by defects in cardiolipin synthesis.
1. Yoshihiro Harada, Shuuichi Nishikawa, Koji Yamano, Megumi Kamiya, Takuya Shiota, and Toshiya Endo (Department of Chemistry, Graduate School of Science, Nagoya University), Takuya Kuroda, Osamu Kuge (Department of Chemistry, Faculty of Sciences, Kyushu University), Hiromi Sesaki (Department of Cell Biology, The Johns Hopkins University School of Medicine), Kenichiro Imai, Kentaro Tomii (Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology).
Associate Professor Yasushi Tamura
Associate Professor Yasushi Tamura began his research on mitochondrial lipids due to his interest in understanding how mitochondrial membranes maintain their characteristic lipid composition. It was previously believed that only one synthetic enzyme of cardiolipin functioned in both mitochondria and the endoplasmic reticulum, but he came to question this generally accepted belief based on his experience with working on protein transport systems during his Ph.D work (A protein generally functions in a specific cellular compartment). He ascertained that the theory was incorrect and refuted it in experiments, and discovered the function of Tam41.
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