title: Deficiency of essential GTP-binding protein ObgE in Escherichia coli inhibits chromosome partition.
abstract: GTP-binding proteins are involved in cell proliferation, development, signal transduction, protein elongation, etc. and construct the GTPase superfamily, whose structures and sequence motifs (G-1 to G-5) are highly conserved from prokaryote to eukaryote. Obg of Bacillus subtilis and Obg homologues of other bacteria belong to the GTPase superfamily and have been suggested as being essential for cell growth, development and monitoring of intracellular levels of GTP. We identified the Obg homologue in Escherichia coli, a protein previously known as YhbZ, which we have renamed ObgE. Double cross-over experiments showed that the obgE gene is essential for growth in E. coli. From characterization of the obgE temperature-sensitive mutant, we found that DNA replication was not inhibited, that the nucleoids did not partition and instead remained in the middle of cell, and that the cells elongated. Overproduction of ObgE also resulted in aberrant chromosome segregation. These data suggested that ObgE is involved directly or indirectly in E. coli chromosome partitioning. Characterization studies showed that ObgE is abundant in normal cells, partially associated with the membrane and does not associate with ribosomes such as in Obg of B. subtilis. We purified ObgE protein from a cell extract of E. coli, and the purified ObgE had GTPase activity and DNA-binding ability.
authors.affiliation: The Institute for Virus Research, Kyoto University, Shogoin-Kawaracho, Sakyo-Ku, Kyoto 606-8507, Japan.
authors.forename: G
authors.initials: G
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Moriya
authors.forename: C
authors.initials: C
authors.lastname: Wada
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002876:Chromosomes, Bacterial / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial; D020043:Genes, Essential; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins; D009154:Mutation; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D029968:Escherichia coli Proteins; C090542:Obg GTP-binding protein, Bacteria; C108621:CgtA protein, bacteria; D019204:GTP-Binding Proteins; C491572:ObgE protein, E coli; D020559:Monomeric GTP-Binding Proteins