Unique topology of the internal repeats in the cardiac Na+/Ca2+ exchanger

FEBS Lett. 1999 Mar 12;446(2-3):264-8. doi: 10.1016/s0014-5793(99)00218-5.


Hydropathy analysis predicts 11 transmembrane helices in the cardiac Na+/Ca2+ exchanger. Using cysteine susceptibility analysis and epitope tagging, we here studied the membrane topology of the exchanger, in particular of the highly conserved internal alpha-1 and alpha-2 repeats. Unexpectedly, we found that the connecting loop in the alpha-1 repeat forms a re-entrant membrane loop with both ends facing the extracellular side and one residue (Asn-125) being accessible from the inside and that the region containing the alpha-2 repeat is mostly accessible from the cytoplasm. Together with other data, we propose that the exchanger may consist of nine transmembrane helices.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Dogs
  • Heart
  • Humans
  • Models, Biological
  • Mutagenesis
  • Proto-Oncogene Proteins c-fos / genetics
  • Proto-Oncogene Proteins c-fos / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sodium-Calcium Exchanger / genetics
  • Sodium-Calcium Exchanger / metabolism*


  • Proto-Oncogene Proteins c-fos
  • Recombinant Fusion Proteins
  • Sodium-Calcium Exchanger
  • sodium-calcium exchanger 1