title: A new heat shock gene, AgsA, which encodes a small chaperone involved in suppressing protein aggregation in Salmonella enterica serovar typhimurium.
abstract: We discovered a novel small heat shock protein (sHsp) named AgsA (aggregation-suppressing protein) in the thermally aggregated fraction from a Salmonella enterica serovar Typhimurium dnaK-null strain. The -10 and -35 regions upstream of the transcriptional start site of the agsA gene are characteristic of sigma(32)- and sigma(72)-dependent promoters. AgsA was strongly induced by high temperatures. The similarity between AgsA and the other two sHsps of Salmonella serovar Typhimurium, IbpA and IbpB, is rather low (around 30% amino acid sequence identity). Phylogenetic analysis suggested that AgsA arose from an ancient gene duplication or amplification at an early evolutionary stage of gram-negative bacteria. Here we show that overproduction of AgsA partially complements the DeltadnaK52 thermosensitive phenotype and reduces the amount of heat-aggregated proteins in both DeltadnaK52 and DeltarpoH mutants of Escherichia coli. These data suggest that AgsA is an effective chaperone capable of preventing aggregation of nonnative proteins and maintaining them in a state competent for refolding in Salmonella serovar Typhimurium at high temperatures.
authors.affiliation: Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Inage-ku, Chiba 263-8522, Japan. tomoyasu@p.chiba-u.ac.jp
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Tomoyasu
authors.forename: Akiko
authors.initials: A
authors.lastname: Takaya
authors.forename: Tomomi
authors.initials: T
authors.lastname: Sasaki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nagase
authors.forename: Reiko
authors.initials: R
authors.lastname: Kikuno
authors.forename: Mizue
authors.initials: M
authors.lastname: Morioka
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018833:Chaperonins / Q000096:biosynthesis / Q000235:genetics*; D004926:Escherichia coli / Q000378:metabolism; D005798:Genes, Bacterial; D006358:Hot Temperature; D008969:Molecular Sequence Data; D010802:Phylogeny; D017510:Protein Folding; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D018833:Chaperonins