The structure of CorA: a Mg(2+)-selective channel.
The crystal structure of a closed form of the CorA Mg2+ transporter from Thermatoga maritima completes a set of representative structures of transport systems for all of the major biological elements, Mg2+, Ca2+, Na+, K+ and Cl-. The CorA monomer has a C-terminal membrane domain containing two transmembrane segments and a large N-terminal cytoplasmic soluble domain. In the membrane, CorA forms a homopentamer shaped like a funnel. Comparison of the structure of CorA with that of other ion channels and transporters suggests numerous common features, but, as might be predicted from the unique chemistry of the Mg2+ cation, the structure of CorA has several unusual features. Among these are initial binding in the periplasm of a fully hydrated Mg2+ ion; a ring of positive charge external to the ion-conduction pathway at the cytosolic membrane interface; and highly negatively charged helices in the cytosolic domain that appear capable of interacting with the ring of positive charge to facilitate Mg2+ entry. Finally, there are bound Mg2+ ions in the cytosolic domain that are well placed to control the interaction of the ring of positive charge and the negatively charged helices, and thus control Mg2+ entry.
Maguire
Michael E
ME
Department of Pharmacology, Case School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA. mem6@po.cwru.edu
D001419:Bacteria / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D007473:Ion Channels / Q000737:chemistry* / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*
D007473:Ion Channels; D008274:Magnesium