title: Biosynthesis of riboflavin. Lumazine synthase of Escherichia coli.
abstract: A gene located at 443 kilobases on the Escherichia coli chromosome (subsequently designated ribE) was expressed in a recombinant E. coli strain and was shown to code for the enzyme 6, 7-dimethyl-8-ribityllumazine synthase. The recombinant enzyme was purified to homogeneity. The protein is an icosahedral capsid of 60 subunits with a mass of about 1 MDa as shown by hydrodynamic studies and by electron microscopy. In contrast to the icosahedral lumazine synthase-riboflavin synthase complex of Bacillus subtilis, the lumazine synthase of E. coli is not physically associated with another enzyme of the riboflavin pathway, and the core of the icosahedral capsid is empty. The RIB4 gene of Saccharomyces cerevisiae was also expressed to a high level (about 40% of cellular protein) in E. coli. The recombinant protein is a pentamer of 90 kDa. An insertion of 4 amino acids into helix alpha4 is likely to hinder the formation of an icosahedral capsid by the yeast protein. The kinetic properties of lumazine synthase of E. coli, B. subtilis, and S. cerevisiae are similar.
authors.affiliation: Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, D-85747 Garching, Federal Republic of Germany.
authors.forename: S
authors.initials: S
authors.lastname: Mörtl
authors.forename: M
authors.initials: M
authors.lastname: Fischer
authors.forename: G
authors.initials: G
authors.lastname: Richter
authors.forename: J
authors.initials: J
authors.lastname: Tack
authors.forename: S
authors.initials: S
authors.lastname: Weinkauf
authors.forename: A
authors.initials: A
authors.lastname: Bacher
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016366:Open Reading Frames; D012256:Riboflavin / Q000096:biosynthesis*; D012258:Riboflavin Synthase / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D016415:Sequence Alignment
chemical_list: D009097:Multienzyme Complexes; C044822:6,7-dimethyl-8-ribityllumazine synthase; D012258:Riboflavin Synthase; D012256:Riboflavin