The mitochondrial calcium uniporter (MCU) complex is a highly-selective calcium channel. This complex consists of MCU, mitochondrial calcium uptake proteins (MICUs), MCU regulator 1 (MCUR1), essential MCU regulator element (EMRE), etc. MCU, which is the pore-forming subunit, has 2 highly conserved coiled-coil domains (CC1 and CC2); however, their functional roles are unknown. The yeast expression system of mammalian MCU and EMRE enables precise reconstitution of the properties of the mammalian MCU complex in yeast mitochondria. Using the yeast expression system, we here showed that, when MCU mutant lacking CC1 or CC2 was expressed together with EMRE in yeast, their mitochondrial Ca2+-uptake function was lost. Additionally, point mutations in CC1 or CC2, which were expected to prevent the formation of the coiled coil, also disrupted the Ca2+-uptake function. Thus, it is essential for the Ca2+ uptake function of MCU that the coiled-coil structure be formed in CC1 and CC2. The loss of function of those mutated MCUs was also observed in the mitochondria of a yeast strain lacking the yeast MCUR1 homolog. Also, in the D. discoideum MCU, which has EMRE-independent Ca2+-uptake function, the deletion of either CC1 or CC2 caused the loss of function. These results indicated that the critical functions of CC1 and CC2 were independent of other regulatory subunits such as MCUR1 and EMRE, suggesting that CC1 and CC2 might be essential for pore formation by MCUs themselves. Based on the tetrameric structure of MCU, we discussed the functional roles of the coiled-coil domains of MCU.

中文翻译：

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MCU的卷曲螺旋结构域在线粒体钙摄取中的功能分析。

线粒体钙单向转运蛋白（MCU）复合物是高度选择性的钙通道。该复合物由MCU，线粒体钙摄取蛋白（MICU），MCU调节剂1（MCUR1），MCU必需调节剂元件（EMRE）等组成。MCU是成孔亚基，具有2个高度保守的卷曲螺旋结构域（ CC1和CC2）；但是，它们的功能角色尚不清楚。哺乳动物MCU和EMRE的酵母表达系统能够精确重建酵母线粒体中哺乳动物MCU复合物的特性。使用酵母表达系统，我们在这里表明，当缺少CC1或CC2的MCU突变体与EMRE在酵母中一起表达时，它们的线粒体Ca2 +摄取功能就会丧失。此外，CC1或CC2中的点突变有望阻止线圈的形成，还破坏了Ca2 +的吸收功能。因此，对于MCU的Ca2 +吸收功能至关重要的是，在CC1和CC2中形成螺旋线圈结构。在缺乏酵母MCUR1同源物的酵母菌株的线粒体中也观察到那些突变的MCU的功能丧失。同样，在具有不依赖于EMRE的Ca2 +摄取功能的D. discoideum MCU中，CC1或CC2的缺失会导致功能丧失。这些结果表明，CC1和CC2的关键功能独立于其他调控亚基，例如MCUR1和EMRE，这表明CC1和CC2对于MCU自身形成孔可能是必不可少的。基于MCU的四聚体结构，我们讨论了MCU的螺旋线圈结构域的功能角色。CC1和CC2中形成螺旋线圈结构对于MCU的Ca2 +吸收功能至关重要。在缺乏酵母MCUR1同源物的酵母菌株的线粒体中也观察到那些突变的MCU的功能丧失。同样，在具有不依赖于EMRE的Ca2 +摄取功能的D. discoideum MCU中，CC1或CC2的缺失会导致功能丧失。这些结果表明，CC1和CC2的关键功能独立于其他调节亚基，例如MCUR1和EMRE，这表明CC1和CC2对于MCU自身形成孔可能是必不可少的。基于MCU的四聚体结构，我们讨论了MCU的螺旋线圈结构域的功能角色。CC1和CC2中形成螺旋线圈结构对于MCU的Ca2 +吸收功能至关重要。在缺乏酵母MCUR1同源物的酵母菌株的线粒体中也观察到那些突变的MCU的功能丧失。同样，在具有不依赖于EMRE的Ca2 +吸收功能的D. discoideum MCU中，CC1或CC2的缺失会导致功能丧失。这些结果表明，CC1和CC2的关键功能独立于其他调节亚基，例如MCUR1和EMRE，这表明CC1和CC2对于MCU自身形成孔可能是必不可少的。基于MCU的四聚体结构，我们讨论了MCU的螺旋线圈结构域的功能角色。在缺乏酵母MCUR1同源物的酵母菌株的线粒体中也观察到那些突变的MCU的功能丧失。同样，在具有不依赖于EMRE的Ca2 +摄取功能的D. discoideum MCU中，CC1或CC2的缺失会导致功能丧失。这些结果表明，CC1和CC2的关键功能独立于其他调节亚基，例如MCUR1和EMRE，这表明CC1和CC2对于MCU自身形成孔可能是必不可少的。基于MCU的四聚体结构，我们讨论了MCU的螺旋线圈结构域的功能角色。在缺乏酵母MCUR1同源物的酵母菌株的线粒体中也观察到那些突变的MCU的功能丧失。同样，在具有不依赖于EMRE的Ca2 +摄取功能的D. discoideum MCU中，CC1或CC2的缺失会导致功能丧失。这些结果表明，CC1和CC2的关键功能独立于其他调节亚基，例如MCUR1和EMRE，这表明CC1和CC2对于MCU自身形成孔可能是必不可少的。基于MCU的四聚体结构，我们讨论了MCU的螺旋线圈结构域的功能角色。这些结果表明，CC1和CC2的关键功能独立于其他调节亚基，例如MCUR1和EMRE，这表明CC1和CC2对于MCU自身形成孔可能是必不可少的。基于MCU的四聚体结构，我们讨论了MCU的螺旋线圈结构域的功能角色。这些结果表明，CC1和CC2的关键功能独立于其他调节亚基，例如MCUR1和EMRE，这表明CC1和CC2对于MCU自身形成孔可能是必不可少的。基于MCU的四聚体结构，我们讨论了MCU的螺旋线圈结构域的功能角色。