title: Dissection of a (betaalpha)8-barrel enzyme into two folded halves.
abstract: The (betaalpha)8-barrel, which is the most frequently encountered protein fold, is generally considered to consist of a single structural domain. However, the X-ray structure of the imidazoleglycerol phosphate synthase (HisF) from Thermotoga maritima has identified it as a (betaalpha) 8-barrel made up of two superimposable subdomains (HisF-N and HisF-C). HisF-N consists of the four N-terminal (betaalpha) units and HisF-C of the four C-terminal (betaalpha) units. It has been postulated, therefore, that HisF evolved by tandem duplication and fusion from an ancestral half-barrel. To test this hypothesis, HisF-N and HisF-C were produced in Escherichia coli, purified and characterized. Separately, HisF-N and HisF-C are folded proteins, but are catalytically inactive. Upon co-expression in vivo or joint refolding in vitro, HisF-N and HisF-C assemble to the stoichiometric and catalytically fully active HisF-NC complex. These findings support the hypothesis that the (betaalpha)8-barrel of HisF evolved from an ancestral half-barrel and have implications for the folding mechanism of the members of this large protein family.
authors.affiliation: Abteilung Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstr. 8, D-37077 Göttingen, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Höcker
authors.forename: S
authors.initials: S
authors.lastname: Beismann-Driemeyer
authors.forename: S
authors.initials: S
authors.lastname: Hettwer
authors.forename: A
authors.initials: A
authors.lastname: Lustig
authors.forename: R
authors.initials: R
authors.lastname: Sterner
mesh_terms: D000595:Amino Acid Sequence; D000619:Aminohydrolases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002384:Catalysis; D002850:Chromatography, Gel; D002942:Circular Dichroism; D019281:Dimerization; D019143:Evolution, Molecular; D020440:Gene Duplication; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D013816:Thermodynamics; D020124:Thermotoga maritima / Q000201:enzymology* / Q000235:genetics; D014461:Ultracentrifugation
chemical_list: D011993:Recombinant Fusion Proteins; C087227:imidazole glycerol phosphate synthase; D000619:Aminohydrolases