Inhibition of SERCA Ca2+ pumps by 2-aminoethoxydiphenyl borate (2-APB). 2-APB reduces both Ca2+ binding and phosphoryl transfer from ATP, by interfering with the pathway leading to the Ca2+-binding sites

Eur J Biochem. 2002 Aug;269(15):3678-87. doi: 10.1046/j.1432-1033.2002.03060.x.


2-Aminoethoxydiphenyl Borate (2-APB) has been extensively used recently as a membrane permeable modulator of inositol-1,4,5-trisphosphate-sensitive Ca2+ channels and store-operated Ca2+ entry. Here, we report that 2-APB is also an inhibitor of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) Ca2+ pumps, and additionally increases ion leakage across the phospholipid bilayer. Therefore, we advise caution in the interpretation of results when used in Ca2+ signalling experiments. The inhibition of 2-APB on the SERCA Ca2+ pumps is isoform-dependent, with SERCA 2B being more sensitive than SERCA 1A (IC50 values for inhibition being 325 and 725 micro m, respectively, measured at pH 7.2). The Ca2+-ATPase is also more potently inhibited at lower pH (IC50 = 70 micro m for SERCA1A at pH 6). 2-APB decreases the affinity for Ca2+ binding to the ATPase by more than 20-fold, and also inhibits phosphoryl transfer from ATP (by 35%), without inhibiting nucleotide binding. Activity studies performed using mutant Ca2+-ATPases show that Tyr837 is critical for the inhibition of activity by 2-APB. Molecular modeling studies of 2-APB binding to the Ca2+ ATPase identified two potential binding sites close to this residue, near or between transmembrane helices M3, M4, M5 and M7. The binding of 2-APB to these sites could influence the movement of the loop between M6 and M7 (L6-7), and reduce access of Ca2+ to their binding sites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Animals
  • Boron Compounds / metabolism
  • Boron Compounds / pharmacology*
  • Calcium / metabolism
  • Calcium-Transporting ATPases / antagonists & inhibitors*
  • Calcium-Transporting ATPases / chemistry
  • Calcium-Transporting ATPases / genetics
  • Calcium-Transporting ATPases / metabolism*
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Enzyme Inhibitors / pharmacology*
  • Fluorescence
  • Kinetics
  • Mutation
  • Phosphorylation
  • Protein Conformation
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Tryptophan / chemistry


  • Boron Compounds
  • Enzyme Inhibitors
  • Tryptophan
  • Adenosine Triphosphate
  • 2-aminoethoxydiphenyl borate
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium-Transporting ATPases
  • Calcium