title: Hsc62, Hsc56, and GrpE, the third Hsp70 chaperone system of Escherichia coli.
abstract: Hsc62 is the third Hsp70 homolog of Escherichia coli, which we found previously. Hsc62 is structurally and biochemically similar to DnaK, but hscC gene encoding Hsc62 did not compensate for the defects in the dnaK-null mutant of E. coli MC4100 strain. We cloned the ybeV gene and purified the gene product named Hsc56, a 55,687-Da protein with a J-domain like sequence. Hsc56 stimulated the ATPase activity of only Hsc62 but not those of the other Hsp70 homologs, DnaK and Hsc66. Hsc56 contains the -His-Pro-Glu- sequence corresponding to the His-Pro-Asp motif in DnaJ, which is indispensable for DnaJ to interact with DnaK. Conversion of -His-Pro-Glu- to -Ala-Ala-Ala- abolished the ability of Hsc56 to stimulate the ATPase activity of Hsc62. GrpE, a nucleotide exchange factor for DnaK, also stimulated the ATPase activity of Hsc62 in the presence of Hsc56. Hsc62-Hsc56-GrpE is probably a new Hsp70 chaperone system of E. coli.
authors.affiliation: Institute for Chemical Research, Kyoto University, Uji, Kyoto-Fu 611-0011, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yoshimune
authors.forename: Tohru
authors.initials: T
authors.lastname: Yoshimura
authors.forename: Toru
authors.initials: T
authors.lastname: Nakayama
authors.forename: Tokuzo
authors.initials: T
authors.lastname: Nishino
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Esaki
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000409:Alanine / Q000737:chemistry; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D001426:Bacterial Proteins / Q000502:physiology*; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000502:physiology*; D018698:Glutamic Acid / Q000737:chemistry; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000502:physiology*; D006639:Histidine / Q000737:chemistry; D018832:Molecular Chaperones / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C459098:Hsc56 protein, E coli; D018832:Molecular Chaperones; C114584:hscC protein, E coli; D018698:Glutamic Acid; D006639:Histidine; D011392:Proline; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli; D000409:Alanine