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J. Biol. Chem., Vol. 281, Issue 18, 12436-12444, May 5, 2006

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The Role of the DIF Motif of the DnaJ (Hsp40) Co-chaperone in the Regulation of the DnaK (Hsp70) Chaperone Cycle^*

Gordana Cogelja Cajo¹, B. Erin Horne, William L. Kelley, Françoise Schwager, Costa Georgopoulos, and Pierre Genevaux²

From the Département de Microbiologie et Médecine Moléculaire, Centre Médical Universitaire, 1, rue Michel-Servet, CH-1211, Geneva, Switzerland and the Department of Biochemistry, Tulane University Health Sciences Center, New Orleans, Louisiana 70112

To perform effectively as a molecular chaperone, DnaK (Hsp70) necessitates the assistance of its DnaJ (Hsp40) co-chaperone partner, which efficiently stimulates its intrinsically weak ATPase activity and facilitates its interaction with polypeptide substrates. In this study, we address the function of the conserved glycine- and phenyalanine-rich (G/F-rich) region of the Escherichia coli DnaJ in the DnaK chaperone cycle. We show that the G/F-rich region is critical for DnaJ co-chaperone functions in vivo and that despite a significant degree of sequence conservation among the G/F-rich regions of Hsp40 homologs from bacteria, yeast, or humans, functional complementation in the context of the E. coli DnaJ is limited. Furthermore, we found that the deletion of the whole G/F-rich region is mirrored by mutations in the conserved Asp-Ile/Val-Phe (DIF) motif contained in this region. Further genetic and biochemical analyses revealed that this amino acid triplet plays a critical role in regulation of the DnaK chaperone cycle, possibly by modulating a crucial step subsequent to DnaK-mediated ATP hydrolysis.

Received for publication, October 14, 2005 , and in revised form, February 10, 2006.

^* This work was supported by Swiss National Foundation Grant FN-31-65403 and the Canton of Geneva. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Present address: Laboratory of Microbial Genetics, Division of Molecular Biology, Bijenicka cesta 54, Ruder Boskovic Institute, 10002 Zagreb, Croatia.

² To whom correspondence should be addressed: Département de Microbiologie et Médecine Moléculaire, Centre Médical Universitaire, 1, rue Michel-Servet, CH-1211, Geneva 4, Switzerland. Tel.: 41-22-379-55-14; Fax: 41-22-379-55-02; E-mail: pierre.genevaux{at}medecine.unige.ch.

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