title: Characterization of mutations affecting the Escherichia coli essential GTPase era that suppress two temperature-sensitive dnaG alleles.
abstract: Two suppressor mutations of the temperature-sensitive DNA primase mutant dnaG2903 have been characterized. The gene responsible for suppression, era, encodes an essential GTPase of Escherichia coli. One mutation, rnc-15, is an insertion of an IS1 element within the leader region of the rnc operon and causes a polar defect on the downstream genes of the operon. A previously described polar mutation, rnc-40, was also able to suppress dnaG2903. The other mutation, era-1, causes a single amino acid substitution (P17R) in the G1 region of the GTP-binding domain of Era. Analysis of the GTPase activity of the Era-1 mutant protein showed a four- to five-fold decrease in the ability to convert GTP to GDP. Thus, lowered expression of wild-type Era caused by the polar mutations and reduced GTPase activity caused by the era-1 mutation suppresses dnaG2903 as well as a second dnaG allele, parB. Phenotypic analysis of the era-1 mutant at 25 degrees C showed that 10% of the cells contain four segregated nucleoids, indicative of a delay in cell division. Possible mechanisms of suppression of dnaG and roles for Era are discussed.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Britton
authors.forename: B S
authors.initials: BS
authors.lastname: Powell
authors.forename: D L
authors.initials: DL
authors.lastname: Court
authors.forename: J R
authors.initials: JR
authors.lastname: Lupski
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019915:DNA Primase; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial; D016153:Genes, Suppressor; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D009876:Operon; D010641:Phenotype; D012316:RNA Nucleotidyltransferases / Q000235:genetics*; D016601:RNA-Binding Proteins; D013489:Suppression, Genetic; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D016601:RNA-Binding Proteins; C068027:era protein, E coli; D006160:Guanosine Triphosphate; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins