title: Constitutive expression of small heat shock protein in an htpG disruptant of the Cyanobacterium Synechococcus sp. PCC 7942.
abstract: In cyanobacteria, a disruptant of hspA encoding a small heat shock protein homologue, shows decreased cell growth rates at moderately high temperatures, and loss of both basal and acquired thermo-tolerances, which resemble the phenotype of an htpG disruptant. In vitro studies have shown that both small heat shock protein and Hsp90 can bind and keep non-native proteins in a refolding-competent state under denaturing conditions. The aim of the present study is to elucidate whether constitutive expression of HspA can functionally replace HtpG, a prokaryotic homolog of Hsp90, in the cyanobacterium Synechococcus sp. PCC 7942. HspA did not improve the viability of the htpG disruptant at a lethal temperature, although it did that of the wild type. It did not improve an iron-starved phenotype of the mutant under normal growth conditions, a novel phenotype found in the present study. These results suggest that cellular function of HtpG may differ significantly from that of HspA.
authors.affiliation: Department of Biochemistry and Molecular Biology, Saitama University, Saitama, 338-8570, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kojima
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nakamoto
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D015870:Gene Expression; D005816:Genetic Complementation Test; D018841:HSP90 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006358:Hot Temperature; D009154:Mutation; D046940:Synechococcus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C113725:HspA protein, bacteria; C066720:HtpG protein, bacteria