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J. Biol. Chem., Vol. 280, Issue 24, 22761-22768, June 17, 2005

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The C-terminal (331–376) Sequence of Escherichia coli DnaJ Is Essential for Dimerization and Chaperone Activity

A SMALL ANGLE X-RAY SCATTERING STUDY IN SOLUTION^*

Yuan-yuan Shi, Xin-guo Hong¶||, and Chih-chen Wang**

From the National Laboratory of Biomacromolecules, Institute of Biophysics, Beijing 100101, China, the ^¶Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, China, and the Graduate School of the Chinese Academy of Sciences, China

DnaJ, an Escherichia coli Hsp40 protein composed of 376 amino acid residues, is a chaperone with thioldisulfide oxidoreductase activity. We present here for the first time a small angle x-ray scattering study of intact DnaJ and a truncated version, DnaJ (1–330), in solution. The molecular weight of DnaJ and DnaJ (1–330) determined by both small angle x-ray scattering and size-exclusion chromatography provide direct evidence that DnaJ is a homodimer and DnaJ (1–330) is a monomer. The restored models show that DnaJ is a distorted -shaped dimeric molecule with the C terminus of each subunit forming the central part of the , whereas DnaJ (1–330) exists as a monomer. This indicates that the deletion of the C-terminal 46 residues of DnaJ impairs the association sites, although it does not cause significant conformational changes. Biochemical studies reveal that DnaJ (1–330), while fully retaining its thiol-disulfide oxidoreductase activity, is structurally less stable, and its peptide binding capacity is severely impaired relative to that of the intact molecule. Together, our results reveal that the C-terminal (331–376) residues are directly involved in dimerization, and the dimeric structure of DnaJ is necessary for its chaperone activity but not required for the thiol-disulfide oxidoreductase activity.

Received for publication, April 4, 2005 , and in revised form, April 21, 2005.

^* This work was supported by grants from the China Natural Science Foundation (30270300, 10375075, and 10490190) and the Chinese Academy of Sciences (02C0601). 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.

^|| To whom correspondence may be addressed: Hawaii Institute of Geophysics and Planetology, School of Ocean Earth Science and Technology, University of Hawaii, Honolulu, HI 96822. E-mail: hongxg{at}hawaii.edu. ** To whom correspondence may be addressed: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Rd., Beijing 100101, China. Tel.: 86-10-64888502; Fax: 86-10-64872026; E-mail: chihwang{at}sun5.ibp.ac.cn.

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