title: Structural and functional similarities between a ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO)-like protein from Bacillus subtilis and photosynthetic RuBisCO.
abstract: The sequences classified as genes for various ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBisCO)-like proteins (RLPs) are widely distributed among bacteria, archaea, and eukaryota. In the phylogenic tree constructed with these sequences, RuBisCOs and RLPs are grouped into four separate clades, forms I-IV. In RuBisCO enzymes encoded by form I, II, and III sequences, 19 conserved amino acid residues are essential for CO(2) fixation; however, 1-11 of these 19 residues are substituted with other amino acids in form IV RLPs. Among form IV RLPs, the only enzymatic activity detected to date is a 2,3-diketo-5-methylthiopentyl 1-phosphate (DK-MTP-1-P) enolase reaction catalyzed by Bacillus subtilis, Microcystis aeruginosa, and Geobacillus kaustophilus form IV RLPs. RLPs from Rhodospirillum rubrum, Rhodopseudomonas palustris, Chlorobium tepidum, and Bordetella bronchiseptica were inactive in the enolase reaction. DK-MTP-1-P enolase activity of B. subtilis RLP required Mg(2+) for catalysis and, like RuBisCO, was stimulated by CO(2). Four residues that are essential for the enolization reaction of RuBisCO, Lys(175), Lys(201), Asp(203), and Glu(204), were conserved in RLPs and were essential for DK-MTP-1-P enolase catalysis. Lys(123), the residue conserved in DK-MTP-1-P enolases, was also essential for B. subtilis RLP enolase activity. Similarities between the active site structures of RuBisCO and B. subtilis RLP were examined by analyzing the effects of structural analogs of RuBP on DK-MTP-1-P enolase activity. A transition state analog for the RuBP carboxylation of RuBisCO was a competitive inhibitor in the DK-MTP-1-P enolase reaction with a K(i) value of 103 mum. RuBP and d-phosphoglyceric acid, the substrate and product, respectively, of RuBisCO, were weaker competitive inhibitors. These results suggest that the amino acid residues utilized in the B. subtilis RLP enolase reaction are the same as those utilized in the RuBisCO RuBP enolization reaction.
authors.affiliation: Nara Institute of Science and Technology, Graduate School of Biological Sciences, Ikoma, Nara, Japan.
authors.forename: Yohtaro
authors.initials: Y
authors.lastname: Saito
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ashida
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sakiyama
authors.forename: Nicole Tandeau
authors.initials: NT
authors.lastname: de Marsac
authors.forename: Antoine
authors.initials: A
authors.lastname: Danchin
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Sekowska
authors.forename: Akiho
authors.initials: A
authors.lastname: Yokota
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002384:Catalysis; D018360:Crystallography, X-Ray; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010755:Organophosphates / Q000378:metabolism; D010751:Phosphopyruvate Hydratase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis; D010802:Phylogeny; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: C519707:2,3-diketo-5-methylthiopentane 1-phosphate; D001426:Bacterial Proteins; D010755:Organophosphates; D011994:Recombinant Proteins; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D010751:Phosphopyruvate Hydratase