Structural insights into the mechanisms of Mg2+ uptake, transport, and gating by CorA
Jong, Agnes Jin Oi
Cornvik, Tobias Carl
Date of Issue2012
School of Biological Sciences
Despite the importance of Mg2+ for numerous cellular activities, the mechanisms underlying its import and homeostasis are poorly understood. The CorA family is ubiquitous and is primarily responsible for Mg2+ transport. However, the key questions—such as, the ion selectivity, the transport pathway, and the gating mechanism—have remained unanswered for this protein family. We present a 3.2 Å resolution structure of the archaeal CorA from Methanocaldococcus jannaschii, which is a unique complete structure of a CorA protein and reveals the organization of the selectivity filter, which is composed of the signature motif of this family. The structure reveals that polar residues facing the channel coordinate a partially hydrated Mg2+ during the transport. Based on these findings, we propose a unique gating mechanism involving a helical turn upon the binding of Mg2+ to the regulatory intracellular binding sites, and thus converting a polar ion passage into a narrow hydrophobic pore. Because the amino acids involved in the uptake, transport, and gating are all conserved within the entire CorA family, we believe this mechanism is general for the whole family including the eukaryotic homologs.
Proceedings of the national academy of sciences
© 2012 National Academy of Sciences. This paper was published in Proceedings of the national academy of sciences and is made available as an electronic reprint (preprint) with permission of National Academy of Sciences. The paper can be found at the following official DOI: [http://dx.doi.org/10.1073/pnas.1210076109]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.