Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
Current address: High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.
BMC Biol. 2021 May 10;19(1):98. doi: 10.1186/s12915-021-01036-x.
Mitochondrial respiration is organized in a series of enzyme complexes in turn forming dynamic supercomplexes. In Saccharomyces cerevisiae (baker's yeast), Cox13 (CoxVIa in mammals) is a conserved peripheral subunit of Complex IV (cytochrome c oxidase, CytcO), localized at the interface of dimeric bovine CytcO, which has been implicated in the regulation of the complex.
Here, we report the solution NMR structure of Cox13, which forms a dimer in detergent micelles. Each Cox13 monomer has three short helices (SH), corresponding to disordered regions in X-ray or cryo-EM structures of homologous proteins. Dimer formation is mainly induced by hydrophobic interactions between the transmembrane (TM) helix of each monomer. Furthermore, an analysis of chemical shift changes upon addition of ATP revealed that ATP binds at a conserved region of the C terminus with considerable conformational flexibility.
Together with functional analysis of purified CytcO, we suggest that this ATP interaction is inhibitory of catalytic activity. Our results shed light on the structural flexibility of an important subunit of yeast CytcO and provide structure-based insight into how ATP could regulate mitochondrial respiration.
线粒体呼吸是一系列酶复合物的有序排列，这些酶复合物继而形成动态的超复合物。在酿酒酵母（面包酵母）中，Cox13（哺乳动物中的 CoxVIa）是细胞色素 c 氧化酶（CytcO）复合物 IV 的保守的外周亚基，位于二聚体牛 CytcO 的界面处，其被认为参与复合物的调节。
本文报道了 Cox13 的溶液 NMR 结构，其在去污剂胶束中形成二聚体。每个 Cox13 单体具有三个短螺旋（SH），对应于同源蛋白的 X 射线或 cryo-EM 结构中的无规卷曲区域。二聚体的形成主要是由每个单体的跨膜（TM）螺旋之间的疏水相互作用诱导的。此外，对添加 ATP 时的化学位移变化的分析表明，ATP 结合在 C 末端的保守区域，具有相当大的构象灵活性。
结合对纯化 CytcO 的功能分析，我们认为这种 ATP 相互作用是对催化活性的抑制。我们的结果揭示了酵母 CytcO 重要亚基的结构灵活性，并提供了基于结构的见解，说明 ATP 如何调节线粒体呼吸。
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