1.A.31.1.6
Annexxin of 369 aas.  Schistosomiasis, a major parasitic disease of humans, is second only to malaria in its global impact. The disease is caused by digenean trematodes that infest the vasculature of their human hosts. These flukes are limited externally by a body wall composed of a syncytial epithelium, the apical surface membrane, a parasitism-adapted dual membrane complex. Annexins are important for the stability of this apical membrane system. Leow et al. 2013 presented the first structural and immunobiochemical characterization of an annexin from Schistosoma mansoni. The crystal structures of annexin B22 (4MDV and 4MDU) in the apo and Ca²⁺ bound forms confirmed the presence of the previously predicted α-helical segment in the II/III linker and revealed a covalently linked head-to-head dimer. The dimeric arrangement revealed a non-canonical membrane binding site and a probable binding groove opposite the binding site. Annexin B22 expression correlated with life stages of the parasite that possess the syncytial tegument layer, and ultrastructural localization by immuno-electron microscopy confirmed the occurrence of annexins in the tegument of S. mansoni.