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Journal of Bacteriology, June 2005, p. 4207-4213, Vol. 187, No. 12
0021-9193/05/$08.00+0     doi:10.1128/JB.187.12.4207-4213.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Defense against Protein Carbonylation by DnaK/DnaJ and Proteases of the Heat Shock Regulon

Åsa Fredriksson,1 Manuel Ballesteros,2 Sam Dukan,3 and Thomas Nyström1*

Department of Cell and Molecular Biology, Microbiology, Göteborg University, Box 462, 405 30 Göteborg, Sweden,1 Centro Andaluz de Biologia del Desarrollo (CABD), University "Pablo de Olavide," Ctra Utrera km1, ES-41013 Seville, Spain,2 Laboratoire de Chimie Bactérienne, CNRS-UPR9043, 31 Chemin Joseph Aiguier, 13402 Marseille, France3

Received 21 January 2005/ Accepted 8 March 2005

Protein carbonylation is an irreversible oxidative modification that increases during organism aging and bacterial growth arrest. We analyzed whether the heat shock regulon has a role in defending Escherichia coli cells against this deleterious modification upon entry into stationary phase. Providing the cell with ectopically elevated levels of the heat shock transcription factor, {sigma}32, effectively reduced stasis-induced carbonylation. Separate overproduction of the major chaperone systems, DnaK/DnaJ and GroEL/GroES, established that the former of these is more important in counteracting protein carbonylation. Deletion of the heat shock proteases Lon and HslVU enhanced carbonylation whereas a clpP deletion alone had no effect. However, ClpP appears to have a role in reducing protein carbonyls in cells lacking Lon and HslVU. Proteomic immunodetection of carbonylated proteins in the wild-type, lon, and hslVU strains demonstrated that the same spectrum of proteins displayed a higher load of carbonyl groups in the lon and hslVU mutants. These proteins included the ß-subunit of RNA polymerase, elongation factors Tu and G, the E1 subunit of the pyruvate dehydrogenase complex, isocitrate dehydrogenase, 6-phosphogluconate dehydrogenase, and serine hydroxymethyltranferase.


* Corresponding author. Mailing address: Department of Cell and Molecular Biology, Microbiology, Medicinaregatan 9C, 413 90 Göteborg, Sweden. Phone: 46 31 7732582. Fax: 46 31 7732599. E-mail: thomas.nystrom{at}gmm.gu.se.


Journal of Bacteriology, June 2005, p. 4207-4213, Vol. 187, No. 12
0021-9193/05/$08.00+0     doi:10.1128/JB.187.12.4207-4213.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.




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