Expression, purification, crystallization and preliminary X-ray diffraction analysis of alpha-11 giardin from Giardia lamblia.

Alpha-11 Giardin, a protein from the annexin superfamily, is a 35.0 kDa protein from the intestinal protozoan parasite Giardia lamblia which triggers a form of diarrhea called giardiasis. Here, the cloning, expression, purification and the crystallization of alpha-11 giardin under two different conditions and in two different space groups is reported. Crystals from the first condition diffracted to 1.1 A and belong to a primitive orthorhombic space group, while crystals from the second condition, which included calcium in the crystallization solution, diffracted to 2.93 A and belong to a primitive monoclinic space group. Determination of the detailed atomic structure of alpha-11 giardin will provide a better insight into its biological function and might establish whether this class of proteins is a potential drug target against giardiasis.