SUBDOMAIN STRUCTURE OF LIPID-BOUND ANNEXIN-V RESOLVED BY ELECTRON IMAGE-ANALYSIS

Two-dimensional crystals of annexin-V bound to lipid layers containing dioleoyl-phosphatidylserine have been obtained in the presence of Ca2+. The crystals diffract to 20 Å resolution and have the symmetry of the plane group p3 (unit cell dimensions: a = b = 94 A ̊, γ = 120 °). Electron image analysis revealed that the crystals are composed of trimers of annexin-V forming triskelion-like motifs. Each annexin-V molecule has a characteristic elongated shape, about 65 Å by 20 Å, when observed perpendicularly to the crystal plane. It is composed of two staggered domains of similar size, about 40 Å by 20 Å. Both domains are made of two sub-domains. The present data suggest that the four resolved sub-domains represent the folding units corresponding to the four 70 amino acid repeating segments characteristic of all annexins. © 1991.