title: Purification, crystallization, and preliminary X-ray diffraction analysis of the Tricorn protease hexamer from Thermoplasma acidophilum.
abstract: Tricorn protease from Thermoplasma acidophilum is a hexameric enzyme; in vivo the hexamers assemble further to form large icosahedral capsids of 14.6 MDa. Recombinant Tricorn protease was purified as an enzymatically active hexamer of 0.72 MDa that formed crystals of octahedral morphology under low-ionic-strength conditions. These crystals belong to space group C2 with unit cell dimensions a = 307.5 A, b = 163.2 A, c = 220.9 A, beta = 105.5 degrees and diffract to 2.2-A resolution using high-brilliance synchrotron radiation. Based on analysis of the self-rotation function and the presence of a pseudo-origin peak in the native Patterson map, a packing model was derived for the complex, comprising 1.5 hexamers per asymmetric unit with a solvent content of 43%. Due to the ninefold noncrystallographic symmetry the Tricorn crystals represent an interesting case for phasing X-ray crystallographic data by electron microscopic phase information.
authors.affiliation: Max-Planck-Institute of Biochemistry, Am Klopferspitz 18a, Martinsried bei München, D-82152, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Bosch
authors.forename: T
authors.initials: T
authors.lastname: Tamura
authors.forename: G
authors.initials: G
authors.lastname: Bourenkov
authors.forename: W
authors.initials: W
authors.lastname: Baumeister
authors.forename: L O
authors.initials: LO
authors.lastname: Essen
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry; D003460:Crystallization; D010450:Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification; D008968:Molecular Conformation; D013822:Thermoplasma / Q000201:enzymology*; D014961:X-Ray Diffraction
chemical_list: D019843:Archaeal Proteins; D010450:Endopeptidases; C102094:tricorn protease