title: Crystal structure of muconolactone isomerase at 3.3 A resolution.
abstract: The crystal structure of muconolactone isomerase from Pseudomonas putida, a unique molecule with ten 96 amino acid subunits and 5-fold, and 2-fold symmetries, has been solved at 3.3 A resolution. The non-crystallographic symmetries were used to refine the initial single isomorphous replacement phases and produce an interpretable 10-fold averaged map. The backbone trace is complete and confirmed by the amino acid sequence fit. Each subunit is composed of a body with two alpha-helices and an antiparallel twisted beta-sheet of four strands, and an extended arm. The helices and the sheet fold to form a two-layered structure with an enclosed hydrophobic core and a partially formed putative active site pocket. The C-terminal arm of another subunit related by a local dyad symmetry extends over the core to complete this pocket. The decameric protein is almost spherical, with the helices forming the external coat. There is a large hydrophilic cavity in the center with open ends along the 5-fold axis. Molecular interactions between subunits are extensive. Each subunit contacts four neighbors and loses nearly 40% of its solvent contact area on oligomerization.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
authors.forename: S K
authors.initials: SK
authors.lastname: Katti
authors.forename: B A
authors.initials: BA
authors.lastname: Katz
authors.forename: H W
authors.initials: HW
authors.lastname: Wyckoff
mesh_terms: D000596:Amino Acids; D001426:Bacterial Proteins; D019748:Carbon-Carbon Double Bond Isomerases; D002384:Catalysis; D007535:Isomerases; D008958:Models, Molecular; D008961:Models, Structural; D011108:Polymers; D011549:Pseudomonas / Q000201:enzymology*; D014961:X-Ray Diffraction
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D011108:Polymers; D007535:Isomerases; D019748:Carbon-Carbon Double Bond Isomerases; C100087:muconolactone delta-isomerase