title: Inorganic polyphosphate stimulates lon-mediated proteolysis of nucleoid proteins in Escherichia coli.
abstract: Inorganic polyphosphate (polyP) accumulates in response to amino acid starvation in Escherichia coli. Previously, we found that the complex formation of Lon with polyP stimulates proteolysis of free ribosomal proteins. In the current studies, we examined the effects of polyP on the degradation of major nucleoid proteins. Fusions of green fluorescent protein with HimA, Fis, HupA, and HupB were clearly associated with polyP in vivo. Lon degraded His-tagged HimA protein only in the presence of polyP in vitro as well as in vivo. Whereas, when HimA and HimD formed a heterodimer, Lon could not degrade it even in the presence of polyP. In addition, Lon degraded His-tagged Fis protein in the presence of polyP. However, in vivo, Lon did not efficiently degrade the Fis protein even when cells accumulated polyP in response to amino acid starvation. It appears that this is due to tighter binding of Fis to DNA than to polyP and resistance of the DNA-Fis to Lon-mediated proteolysis. Indeed, we found that at least a five-fold excess of polyP was necessary to displace DNA from the DNA-Fis complex. Furthermore, Lon degraded His-tagged HupA protein efficiently in the presence of polyP. We also showed that degradation of the translational initiation factor InfC depends on polyP.
authors.affiliation: Department of Molecular Biotechnology, Hiroshima University, Hiroshima, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Kuroda
authors.forename: K
authors.initials: K
authors.lastname: Nomura
authors.forename: N
authors.initials: N
authors.lastname: Takiguchi
authors.forename: J
authors.initials: J
authors.lastname: Kato
authors.forename: H
authors.initials: H
authors.lastname: Ohtake
mesh_terms: D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D035021:Factor For Inversion Stimulation Protein / Q000235:genetics / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D011122:Polyphosphates / Q000378:metabolism*; D049070:Protease La / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; C501034:Fis protein, E coli; D010710:Phosphates; D011122:Polyphosphates; D011993:Recombinant Fusion Proteins; C490937:hupA protein, E coli; C483567:Lon protein, E coli; D049070:Protease La