title: Evidence for local 32 symmetry in homotrimeric riboflavin synthase of Escherichia coli.
abstract: Riboflavin synthase is a trimer of identical 23-kDa subunits. The primary structure is characterized by considerable similarity of the C-terminal and N-terminal parts. Recombinant riboflavin synthase of Escherichia coli and Bacillus subtilis was crystallized by the vapor diffusion method. Crystals of E. coli riboflavin synthase belong to the orthorhombic system, space group P2(1)2(1)2(1), with unit cell dimensions a = 53.2 A, b = 117.6 A, c = 150.9 A, alpha = beta = gamma = 90 degrees. They diffract to better than 3.3 A resolution and have presumably one trimer in the asymmetric unit. The self rotation function indicates local 32 symmetry. Twofold local symmetry is an unexpected result in a trimeric protein. In conjunction with primary structure arguments and mechanistic considerations, we propose that the protein is a pseudohexamer where each of the peptide subunits fold into two topologically similar domains.
authors.affiliation: Karolinska Institute, NOVUM, Center of Structural Biochemistry, Huddinge, Sweden.
authors.forename: W
authors.initials: W
authors.lastname: Meining
authors.forename: G
authors.initials: G
authors.lastname: Tibbelin
authors.forename: R
authors.initials: R
authors.lastname: Ladenstein
authors.forename: S
authors.initials: S
authors.lastname: Eberhardt
authors.forename: M
authors.initials: M
authors.lastname: Fischer
authors.forename: A
authors.initials: A
authors.lastname: Bacher
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics; D003460:Crystallization; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D008958:Models, Molecular; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D012258:Riboflavin Synthase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D011994:Recombinant Proteins; D012258:Riboflavin Synthase