title: Supramolecular complex formation and crystallization of isocitrate dehydrogenase from Thermus thermophilus HB8: preliminary studies with X-Ray crystallography and atomic force microscopy.
abstract: Atomic force microscopy (AFM) observation of a crystal surface of the thermostable isocitrate dehydrogenase (ICDH) from a thermophilic eubacterium, Thermus thermophilus HB8, suggested that the crystal consists of huge homo-complexed ellipsoidal bodies of the protein, with averaged long- and short-axis diameters of 18.6 nm and 10.9 nm respectively. Thick diamond-shaped crystals of about 0.4 mm on the longest axis were obtained by the vapor diffusion method from a solution of 100 mM sodium cacodylate, pH 6.6-8.4, containing 1.4 M sodium acetate as the precipitate, and diffracted X-rays at 3.7 A resolution. The crystals belonged to the monoclinic lattice type with space group C2 and had cell dimensions of a=495.5, b=189.2, c=336.2 A, and beta=126.4 degrees , indicating that an asymmetric unit contained more than 33 molecules with a molecular mass of 54.2 kDa. Calculations based on data obtained by the X-ray method showed good agreement with AFM observation. These results suggest the possibility that the residing T. thermophilus HB8 ICDH molecules are piled one on top another as a preformed supramolecular nano-architecture in the crystal lattice. The system appears suitable for further investigation using a bottom-up approach to the self-associated construction of nano-architectures with proteins.
authors.affiliation: Biological Information Research Center, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan. ishii@ni.aist.go.jp
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Ishii
authors.forename: Kazuo
authors.initials: K
authors.lastname: Umemura
authors.forename: Kentaro
authors.initials: K
authors.lastname: Miyazaki
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods*; D004926:Escherichia coli / Q000235:genetics; D007521:Isocitrate Dehydrogenase / Q000737:chemistry* / Q000302:isolation & purification; D018625:Microscopy, Atomic Force; D008970:Molecular Weight; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D016963:Thermus thermophilus / Q000737:chemistry* / Q000235:genetics; D014961:X-Ray Diffraction
chemical_list: D007521:Isocitrate Dehydrogenase