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Logo of jbcThe Journal of Biological Chemistry
J Biol Chem. 2011 November 25; 286(47): e99978.
PMCID: PMC3220455

View of the Human Na+/H+ Exchanger Regulatory Region Bound to Calmodulin♦

Structure of Human Na+/H+ Exchanger NHE1 Regulatory Region in Complex with Calmodulin and Ca2+

♦ See referenced article, J. Biol. Chem. 2011, 286, 40954–40961

The antiporter NHE1 transports Na+ and H+ in opposite directions in mammalian cells to regulate intracellular pH, salt concentration, and cell volume. Its malfunctions are implicated in some cardiovascular diseases. The Ca2+-binding protein calmodulin (CaM) regulates NHE1 by binding to its C-terminal cytoplasmic domain. Özkan Yildiz and co-workers at the Max Planck Institute of Biophysics in Germany show for the first time a 2.23 Å crystal structure of the NHE1 CaM-binding region complexed with CaM and Ca2+. The investigators found that the C- and N-terminal lobes of CaM bind the first and second helices of the NHE1 binding region, respectively. They also discovered that, when bound to NHE1, CaM adopts an elongated form that resembles its conformation free in solution. Yildiz and colleagues state that the structure helps to understand “the puzzle of intricate inter- and intramolecular interactions that regulate the activity of this essential antiporter.”

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The schematic shows how NHE1 activity is controlled by calmodulin. PMS, proton modifier site.

Articles from The Journal of Biological Chemistry are provided here courtesy of American Society for Biochemistry and Molecular Biology