Structure of a new crystal form of human Hsp70 ATPase domain

Hsp70 proteins are highly conserved proteins induced by heat shock and other stress conditions. An ATP-binding domain of human Hsp70 protein has been crystallized in two major morphological forms at pH 7.0 in the presence of PEG 8000 and CaCl₂. Both crystal forms belong to the orthorhombic space group P2₁2₁2₁, but show no resemblance in unit-cell parameters. Analysis of the crystal structures for both forms shows a 1-2 Å shift of one of the subdomains of the protein. This conformational change could reflect a 'natural' flexibility of the protein which might be relevant to ATP binding and may facilitate the interaction of other proteins with Hsp70 protein.