title: Molecules of Escherichia coli MobB assemble into densely packed hollow cylinders in a crystal lattice with 75% solvent content.
abstract: The crystal structure of Escherichia coli MobB, an enzyme involved in the final step of molybdenum-cofactor biosynthesis, forms intertwined dimers. Each molecule consists of two segments and requires the second monomer for stable folding. Dimerization buries a quarter of the solvent-accessible area of the monomer. These dimers assemble into a hexagonal lattice with P6(4)22 symmetry and occupy only approximately 25% of the unit-cell volume. The symmetry-related dimers associate tightly into a helical structure with a diameter of 250 A and a pitch of 98 A. Two such helices are intertwined, shifted by 49 A along the sixfold axis. Within the crystal, these helices form thin-walled cylinders with an external diameter of 250 A and an internal diameter of 190 A. Their center is filled with solvent. These cylinders pack closely together, forming a hexagonal lattice with the highest possible packing density. This arrangement of dimers allows extensive intermolecular contacts with 75% solvent content in the crystal.
authors.affiliation: Department of Biochemistry, McGill University, Canada.
authors.forename: S Erumbi
authors.initials: SE
authors.lastname: Rangarajan
authors.forename: Ante
authors.initials: A
authors.lastname: Tocilj
authors.forename: Yunge
authors.initials: Y
authors.lastname: Li
authors.forename: Pietro
authors.initials: P
authors.lastname: Iannuzzi
authors.forename: Allan
authors.initials: A
authors.lastname: Matte
authors.forename: Miroslaw
authors.initials: M
authors.lastname: Cygler
mesh_terms: D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D012645:Selenomethionine / Q000737:chemistry; D012997:Solvents; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; C490938:MobB protein, E coli; C099206:MobB protein, bacteria; D011994:Recombinant Proteins; D012997:Solvents; D015534:Trans-Activators; D012645:Selenomethionine