title: Role of Streptococcus intermedius DnaK chaperone system in stress tolerance and pathogenicity.
abstract: Streptococcus intermedius is a facultatively anaerobic, opportunistic pathogen that causes purulent infections and abscess formation. The DnaK chaperone system has been characterized in several pathogenic bacteria and seems to have important functions in stress resistance and pathogenicity. However, the role of DnaK in S. intermedius remains unclear. Therefore, we constructed a dnaK knockout mutant that exhibited slow growth, thermosensitivity, accumulation of GroEL in the cell, and reduced cytotoxicity to HepG2 cells. The level of secretion of a major pathogenic factor, intermedilysin, was not affected by dnaK mutation. We further examined the function and property of the S. intermedius DnaK chaperone system by using Escherichia coli ΔdnaK and ΔrpoH mutant strains. S. intermedius DnaK could not complement the thermosensitivity of E. coli ΔdnaK mutant. However, the intact S. intermedius DnaK chaperone system could complement the thermosensitivity and acid sensitivity of E. coli ΔdnaK mutant. The S. intermedius DnaK chaperone system could regulate the activity and stability of the heat shock transcription factor σ(32) in E. coli, although S. intermedius does not utilize σ(32) for heat shock transcription. The S. intermedius DnaK chaperone system was also able to efficiently eliminate the aggregated proteins from ΔrpoH mutant cells. Overall, our data showed that the S. intermedius DnaK chaperone system has important functions in quality control of cellular proteins but has less participation in the modulation of expression of pathogenic factors.
authors.affiliation: Department of Biological Science and Technology, Institute of Technology and Science, The University of Tokushima Graduate School, 2 chome, Minami-josanjima, Tokushima 770-8506, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Tomoyasu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tabata
authors.forename: Hidenori
authors.initials: H
authors.lastname: Imaki
authors.forename: Keigo
authors.initials: K
authors.lastname: Tsuruno
authors.forename: Aya
authors.initials: A
authors.lastname: Miyazaki
authors.forename: Kenji
authors.initials: K
authors.lastname: Sonomoto
authors.forename: Robert Alan
authors.initials: RA
authors.lastname: Whiley
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nagamune
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001430:Bacteriocins / Q000378:metabolism / Q000633:toxicity; D018834:Chaperonin 60 / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D055786:Gene Knockout Techniques; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D016415:Sequence Alignment; D034367:Streptococcus intermedius / Q000378:metabolism* / Q000472:pathogenicity*; D013312:Stress, Physiological
chemical_list: D001426:Bacterial Proteins; D001430:Bacteriocins; D018834:Chaperonin 60; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; C403910:intermedilysin protein, Streptococcus intermedius; C063842:dnaK protein, E coli