Crystallization of p68 on lipid monolayers and as three-dimensional single crystals

J Mol Biol. 1989 Mar 5;206(1):213-9. doi: 10.1016/0022-2836(89)90534-2.


Two-dimensional crystals of p68, a Ca2+ -binding protein that has homology with members of the lipocortin/calpactin family, were obtained by interaction with a phospholipid monolayer. By measuring surface pressure at constant surface area, p68 was found to interact in a Ca2+ -dependent manner specifically with phosphatidylethanolamine, less so with phosphatidylserine and not at all with phosphatidylcholine. With dimyristoyl-phosphatidylethanolamine, two-dimensional crystalline arrays were formed. Image analysis of electron micrographs of these crystals, which diffracted to about 50 A, revealed p3 symmetry with a unit cell of about 178 A by 178 A; the protein densities showed a two-domain structure giving a cylindrical molecule of about 100 A by 35 A diameter packed as trimers. Three-dimensional microcrystals obtained without lipid or Ca2+ were suitable for electron microscopy and gave a tetragonal unit cell of about 256 A by 68 A. The implications of these observations on the structure and lipid specificity of p68 binding are discussed.

MeSH terms

  • Annexin A6
  • Calcium-Binding Proteins* / metabolism
  • Crystallization
  • Humans
  • Phospholipids* / metabolism
  • X-Ray Diffraction


  • Annexin A6
  • Calcium-Binding Proteins
  • Phospholipids