Characterization of the calcium-binding sites of calcineurin B

Lazaros T. Kakalis, Michael Kennedy, Robert Sikkink, Frank Rusnak, Ian M. Armitage*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


Calcineurin (CaN) is a calcium- and calmodulin-dependent serine/threonine phosphatase whose inhibition by the immunosuppressant-immunophilin complexes (cyclosporin-cyclophilin and FK506-FKBP) is considered key to the mechanism of immunosuppression. CaN is a heterodimer, consisting of a 59 kDa catalytic subunit (A) and a 19 kDa calcium-binding regulatory subunit (B). The latter is postulated to harbor four calcium binding domains of the EF hand type. The titration of the CaN B apoprotein with the isomorphic Cd2+ was followed by 113Cd NMR and these data support one high-affinity metal binding site and three lower-affinity ones. Flow dialysis data with Ca2+ indicate one high affinity calcium binding site with Kd ∼ 2.4 × 10-8 M and three other sites with Kd ∼ 1.5 × 10-5 M. The chemical shifts of all four 113Cd resonances (-75, -93, -106 and -119 ppm) are in the same range as found in other 113Cd substituted calcium-binding proteins, and are indicative of all-oxygen coordination of pentagonal bipyramidal geometry.

Original languageEnglish (US)
Pages (from-to)55-58
Number of pages4
JournalFEBS Letters
Issue number1
StatePublished - Mar 27 1995


  • Cadmium-113 NMR
  • Calcineurin
  • Calcium binding
  • EF hand

ASJC Scopus subject areas

  • Genetics
  • Molecular Biology
  • Biophysics
  • Structural Biology
  • Biochemistry
  • Cell Biology


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