Department of Biochemistry & Centre de Recherche en Biologie Structurale, McGill University, Montréal, QC, Canada.
Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada.
Nat Commun. 2021 Jun 29;12(1):4028. doi: 10.1038/s41467-021-24282-7.
CNNM/CorB proteins are a broadly conserved family of integral membrane proteins with close to 90,000 protein sequences known. They are associated with Mg transport but it is not known if they mediate transport themselves or regulate other transporters. Here, we determine the crystal structure of an archaeal CorB protein in two conformations (apo and Mg-ATP bound). The transmembrane DUF21 domain exists in an inward-facing conformation with a Mg ion coordinated by a conserved π-helix. In the absence of Mg-ATP, the CBS-pair domain adopts an elongated dimeric configuration with previously unobserved domain-domain contacts. Hydrogen-deuterium exchange mass spectrometry, analytical ultracentrifugation, and molecular dynamics experiments support a role of the structural rearrangements in mediating Mg-ATP sensing. Lastly, we use an in vitro, liposome-based assay to demonstrate direct Mg transport by CorB proteins. These structural and functional insights provide a framework for understanding function of CNNMs in Mg transport and associated diseases.
CNNM/CorB 蛋白是一类广泛保守的整合膜蛋白家族，已知其拥有近 90000 个蛋白序列。它们与 Mg 转运有关，但尚不清楚它们是否自身介导转运或调节其他转运蛋白。在这里，我们确定了两种构象（apo 和 Mg-ATP 结合）的古菌 CorB 蛋白的晶体结构。跨膜 DUF21 结构域存在于向内的构象中，一个 Mg 离子由保守的π-螺旋配位。在没有 Mg-ATP 的情况下，CBS 对结构域采用以前未观察到的拉长二聚体构型，存在结构域-结构域接触。氢氘交换质谱、分析超速离心和分子动力学实验支持结构重排在介导 Mg-ATP 感应中的作用。最后，我们使用基于脂质体的体外测定来证明 CorB 蛋白的直接 Mg 转运。这些结构和功能上的见解为理解 CNNMs 在 Mg 转运和相关疾病中的功能提供了框架。
