title: Pyruvate carboxylase from Rhizobium etli: mutant characterization, nucleotide sequence, and physiological role.
abstract: Pyruvate carboxylase (PYC), a biotin-dependent enzyme which catalyzes the conversion of pyruvate to oxaloacetate, was hypothesized to play an important anaplerotic role in the growth of Rhizobium etli during serial subcultivation in minimal media containing succinate (S. Encarnación, M. Dunn, K. Willms, and J. Mora, J. Bacteriol. 177:3058-3066, 1995). R. etli and R. tropici pyc::Tn5-mob mutants were selected for their inability to grow in minimal medium with pyruvate as a sole carbon source. During serial subcultivation in minimal medium containing 30 mM succinate, the R. etli parent and pyc mutant strains exhibited similar decreases in growth rate with each subculture. Supplementation of the medium with biotin prevented the growth decrease of the parent but not the mutant strain, indicating that PYC was necessary for the growth of R. etli under these conditions. The R. tropici pyc mutant grew normally in subcultures regardless of biotin supplementation. The symbiotic phenotypes of the pyc mutants from both species were similar to those of the parent strains. The R. etli pyc was cloned, sequenced, and found to encode a 126-kDa protein of 1,154 amino acids. The deduced amino acid sequence is highly homologous to other PYC sequences, and the catalytic domains involved in carboxylation, pyruvate binding, and biotinylation are conserved. The sequence and biochemical data show that the R. etli PYC is a member of the alpha4, homotetrameric, acetyl coenzyme A-activated class of PYCs.
authors.affiliation: Departamento de Ecología Molecular, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Cuernavaca, Morelos. mike@cifn.unam.mx
authors.forename: M F
authors.initials: MF
authors.lastname: Dunn
authors.forename: S
authors.initials: S
authors.lastname: Encarnación
authors.forename: G
authors.initials: G
authors.lastname: Araíza
authors.forename: M C
authors.initials: MC
authors.lastname: Vargas
authors.forename: A
authors.initials: A
authors.lastname: Dávalos
authors.forename: H
authors.initials: H
authors.lastname: Peralta
authors.forename: Y
authors.initials: Y
authors.lastname: Mora
authors.forename: J
authors.initials: J
authors.lastname: Mora
mesh_terms: D000595:Amino Acid Sequence; D001710:Biotin / Q000494:pharmacology; D003001:Cloning, Molecular; D007887:Fabaceae / Q000382:microbiology; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation; D010641:Phenotype; D010946:Plants, Medicinal; D011487:Protein Conformation; D011766:Pyruvate Carboxylase / Q000145:classification / Q000502:physiology*; D012231:Rhizobium / Q000187:drug effects / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid; D013559:Symbiosis
chemical_list: D013386:Succinates; D001710:Biotin; D019802:Succinic Acid; D011766:Pyruvate Carboxylase