The periplasmic loop provides stability to the open state of the CorA magnesium channel

J Biol Chem. 2012 Aug 10;287(33):27547-55. doi: 10.1074/jbc.M112.371484. Epub 2012 Jun 21.


Crystal structures of the CorA Mg(2+) channel have suggested that metal binding in the cytoplasmic domain stabilizes the pentamer in a closed conformation. The open "metal free" state of the channel is, however, still structurally uncharacterized. Here, we have attempted to map conformational states of CorA from Thermotoga maritima by determining which residues support the pentameric structure in the presence or absence of Mg(2+). We find that when Mg(2+) is present, the pentamer is stabilized by the putative gating sites (M1/M2) in the cytoplasmic domain. Strikingly however, we find that the conserved and functionally important periplasmic loop is vital for the integrity of the pentamer when Mg(2+) is absent from the M1/M2 sites. Thus, although the periplasmic loops were largely disordered in the x-ray structures of the closed channel, our data suggests a prominent role for the loops in stabilizing the open conformation of the CorA channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cation Transport Proteins / chemistry*
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism
  • Crystallography, X-Ray
  • Ion Transport / physiology
  • Magnesium / chemistry*
  • Magnesium / metabolism
  • Periplasm / chemistry
  • Periplasm / genetics
  • Periplasm / metabolism
  • Protein Stability
  • Protein Structure, Quaternary
  • Protein Structure, Secondary
  • Thermotoga maritima / chemistry*
  • Thermotoga maritima / genetics
  • Thermotoga maritima / immunology


  • Cation Transport Proteins
  • Magnesium