Structural highlights
FunctionMRPC_ALKPO Mnh complex is a Na(+)Li(+)/H(+) antiporter involved in Na(+) and/or Li(+) excretion and Na(+) resistance. Na(+)/H(+) antiport consumes a transmembrane electrical potential, and is thus inferred to be electrogenic. Does not transport K(+), Ca(2+) or Mg(2+). Publication Abstract from PubMedMultiple resistance and pH adaptation (Mrp) cation/proton antiporters are essential for growth of a variety of halophilic and alkaliphilic bacteria under stress conditions. Mrp-type antiporters are closely related to the membrane domain of respiratory complex I. We determined the structure of the Mrp antiporter from Bacillus pseudofirmus by electron cryo-microscopy at 2.2 A resolution. The structure resolves more than 99% of the sidechains of the seven membrane subunits MrpA to MrpG plus 360 water molecules, including ~70 in putative ion translocation pathways. Molecular dynamics simulations based on the high-resolution structure revealed details of the antiport mechanism. We find that switching the position of a histidine residue between three hydrated pathways in the MrpA subunit is critical for proton transfer that drives gated trans-membrane sodium translocation. Several lines of evidence indicate that the same histidine-switch mechanism operates in respiratory complex I. Ion transfer mechanisms in Mrp-type antiporters from high resolution cryoEM and molecular dynamics simulations.,Lee Y, Haapanen O, Altmeyer A, Kuhlbrandt W, Sharma V, Zickermann V Nat Commun. 2022 Oct 14;13(1):6091. doi: 10.1038/s41467-022-33640-y. PMID:36241630[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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