title: Identification and characterization of the smbA gene, a suppressor of the mukB null mutant of Escherichia coli.
abstract: The mukB gene encodes a protein involved in chromosome partitioning in Escherichia coli. To study the function of this protein, we isolated from the temperature-sensitive mukB null mutant and characterized 56 suppressor mutants which could grow at 42 degrees C. Ten of the mutants also showed cold-sensitive growth at 22 degrees C. Using one of the cold-sensitive mutants as host, the wild type of the suppressor gene was cloned. The cloned suppressor gene complemented all of the 56 suppressor mutations. DNA sequencing revealed the presence of an open reading frame of 723 bp which could encode a protein of 25,953 Da. The gene product was indeed detected. The previously undiscovered gene, named smbA (suppressor of mukB), is located at 4 min on the E. coli chromosome, between the tsf and frr genes. The smbA gene is essential for cell proliferation in the range from 22 to 42 degrees C. Cells which lacked the SmbA protein ceased macromolecular synthesis. The smbA mutants are sensitive to a detergent, sodium dodecyl sulfate, and they show a novel morphological phenotype under nonpermissive conditions, suggesting a defect in specific membrane sites.
authors.affiliation: Department of Molecular Cell Biology, Kumamoto University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamanaka
authors.forename: T
authors.initials: T
authors.lastname: Ogura
authors.forename: H
authors.initials: H
authors.lastname: Niki
authors.forename: S
authors.initials: S
authors.lastname: Hiraga
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D002455:Cell Division; D002868:Chromosomal Proteins, Non-Histone; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003080:Cold Temperature; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial / Q000235:genetics*; D016153:Genes, Suppressor / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016296:Mutagenesis; D009154:Mutation; D016366:Open Reading Frames; D009996:Osmotic Fragility / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D014166:Transferases
chemical_list: D001426:Bacterial Proteins; D002868:Chromosomal Proteins, Non-Histone; D029968:Escherichia coli Proteins; C067035:MukB protein, E coli; C078379:pyrH protein, E coli; D014166:Transferases