An unusual amino acid substitution within hummingbird cytochrome c oxidase alters a key proton-conducting channel

Hummingbirds in flight exhibit the highest metabolic rate of all vertebrates. The bioenergetic requirements associated with sustained hovering flight raise the possibility of unique amino acid substitutions that would enhance aerobic metabolism. Here, we have identified a non-conservative substitution within the mitochondria-encoded cytochrome c oxidase subunit I (COI) that is fixed within hummingbirds, yet exceedingly rare among other vertebrates. This unusual change is also rare among metazoans, but can be identified in several clades with diverse life histories. We performed atomistic molecular dynamics simulations using bovine and hummingbird COI models, thereby bypassing experimental limitations imposed by the inability to modify mtDNA in a site-specific manner. Intriguingly, our findings suggest that COI amino acid position 153 (bovine numbering system) provides control over the hydration and activity of a key proton channel in COX. We discuss potential phenotypic outcomes linked ...

飞行中的蜂鸟拥有所有脊椎动物中最高的代谢速率。持续悬停飞行所需的生物能量需求，提示存在可增强有氧代谢的独特氨基酸替换。本研究鉴定出一种位于线粒体编码的细胞色素c氧化酶亚基I（cytochrome c oxidase subunit I, COI）内的非保守氨基酸替换，该替换在蜂鸟种群中固定存在，但在其他脊椎动物中极为罕见。这一异常变异在后生动物中同样罕见，但可在多个具有不同生活史的演化支中被检测到。我们利用牛源与蜂鸟的COI模型开展全原子分子动力学模拟，从而规避了无法以位点特异性方式修饰线粒体DNA（mtDNA）的实验局限。有趣的是，我们的研究结果表明，COI氨基酸位点153（采用牛源编号体系）可调控细胞色素c氧化酶（cytochrome c oxidase, COX）中关键质子通道的水合状态与活性。我们将讨论与潜在表型结果相关的……