title: The chemical chaperone proline relieves the thermosensitivity of a dnaK deletion mutant at 42 degrees C.
abstract: Since, like other osmolytes, proline can act as a protein stabilizer, we investigated the thermoprotectant properties of proline in vitro and in vivo. In vivo, elevated proline pools in Escherichia coli (obtained by altering the feedback inhibition by proline of gamma-glutamylkinase, the first enzyme of the proline biosynthesis pathway) restore the viability of a dnaK-deficient mutant at 42 degrees C, suggesting that proline can act as a thermoprotectant for E. coli cells. Furthermore, analysis of aggregated proteins in the dnaK-deficient strain at 42 degrees C by two-dimensional gel electrophoresis shows that high proline pools reduce the protein aggregation defect of the dnaK-deficient strain. In vitro, like other "chemical chaperones," and like the DnaK chaperone, proline protects citrate synthase against thermodenaturation and stimulates citrate synthase renaturation after urea denaturation. These results show that a protein aggregation defect can be compensated for by a single mutation in an amino acid biosynthetic pathway and that an ubiquitously producible chemical chaperone can compensate for a defect in one of the major chaperones involved in protein folding and aggregation.
authors.affiliation: Molécules de Stress, Institut Jacques Monod, Université Paris 7, 2 place Jussieu, 75251 Paris Cedex 05, France.
authors.forename: Madhab K
authors.initials: MK
authors.lastname: Chattopadhyay
authors.forename: Renée
authors.initials: R
authors.lastname: Kern
authors.forename: Michel-Yves
authors.initials: MY
authors.lastname: Mistou
authors.forename: Abhaya M
authors.initials: AM
authors.lastname: Dandekar
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Uratsu
authors.forename: Gilbert
authors.initials: G
authors.lastname: Richarme
mesh_terms: D002950:Citrate (si)-Synthase / Q000737:chemistry; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D006358:Hot Temperature; D018832:Molecular Chaperones / Q000502:physiology*; D011392:Proline / Q000502:physiology*; D011489:Protein Denaturation; D017510:Protein Folding
chemical_list: D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D011392:Proline; D002950:Citrate (si)-Synthase; C063842:dnaK protein, E coli