Calcium-dependent tetramer formation of S100A8 and S100A9 is essential for biological activity

J Mol Biol. 2006 Jun 16;359(4):961-72. doi: 10.1016/j.jmb.2006.04.009. Epub 2006 Apr 21.


S100 proteins comprise the largest family of calcium-binding proteins. Members of this family usually form homo- or heterodimers, which may associate to higher-order oligomers in a calcium-dependent manner. The heterodimers of S100A8 and S100A9 represent the major calcium-binding proteins in phagocytes. Both proteins regulate migration of these cells via modulation of tubulin polymerization. Calcium binding induces formation of (S100A8/S100A9)2 tetramers. The functional relevance of these higher-order oligomers of S100 proteins, however, is not yet clear. To investigate the importance of higher-order oligomerization for S100 proteins, we created a set of mutations within S100A9 (N69A, E78A, N69A+E78A) destroying the high-affinity C-terminal calcium-binding site (EF-hand II). Mutations in EF-hand II did not interfere with formation of the S100A8/S100A9 heterodimer as demonstrated by yeast two-hybrid experiments and pull-down assays. In contrast, mass spectrometric analysis and density gradient centrifugation revealed that calcium-induced association of (S100A8/S100A9)2 tetramers was strictly dependent on a functional EF-hand II in S100A9. Failure of tetramer formation was associated with a lack of functional activity of S100A8/S100A9 complexes in promoting the formation of microtubules. Thus, our data demonstrate that calcium-dependent formation of (S100A8/S100A9)2 tetramers is an essential prerequisite for biological function. This is the first report showing a functional relevance of calcium-induced higher-order oligomerization in the S100 family.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Calcium / metabolism*
  • Calgranulin A / chemistry*
  • Calgranulin A / genetics
  • Calgranulin A / metabolism*
  • Calgranulin B / chemistry*
  • Calgranulin B / genetics
  • Calgranulin B / metabolism*
  • Centrifugation, Density Gradient
  • Dimerization
  • EF Hand Motifs
  • Humans
  • Mutation
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Tubulin / metabolism


  • Calgranulin A
  • Calgranulin B
  • Recombinant Proteins
  • Tubulin
  • Calcium