HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 280, Issue 42, 35424-35432, October 21, 2005

This Article Full Text Full Text (PDF) All Versions of this Article: 280/42/35424    most recent M507240200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kang, S. G. Articles by Maurizi, M. R. Search for Related Content PubMed PubMed Citation Articles by Kang, S. G. Articles by Maurizi, M. R. Social Bookmarking                      What's this?

Human Mitochondrial ClpP Is a Stable Heptamer That Assembles into a Tetradecamer in the Presence of ClpX^*

Sung Gyun Kang1, Mariana N. Dimitrova, Joaquin Ortega¶2, Ann Ginsburg, and Michael R. Maurizi3

From the Laboratory of Cell Biology, NCI, Laboratory of Biochemistry, NHLBI, and ^¶Laboratory of Structural Biology, NIAMS, National Institutes of Health, Bethesda, Maryland 20892

The functional form of ClpP, the proteolytic component of ATP-dependent Clp proteases, is a hollow-cored particle composed of two heptameric rings joined face-to-face forming an aqueous chamber containing the proteolytic active sites. We have found that isolated human mitochondrial ClpP (hClpP) is stable as a heptamer and remains a monodisperse species (s_20,w 7.0 S; M_app 169, 200) at concentrations 3 mg/ml. Heptameric hClpP has no proteolytic activity and very low peptidase activity. In the presence of ATP, hClpX interacts with hClpP forming a complex, which by equilibrium sedimentation measurements has a M_app of 1 x 10⁶. Electron microscopy confirmed that the complex consisted of a double ring of hClpP with an hClpX ring axially aligned on each end. The hClpXP complex has protease activity and greatly increased peptidase activity, indicating that interaction with hClpX affects the conformation of the hClpP catalytic active site. A mutant of hClpP, in which a cysteine residue was introduced into the handle region at the interface between the two rings formed stable tetradecamers under oxidizing conditions but spontaneously dissociated into two heptamers upon reduction. Thus, hClpP rings interact transiently but very weakly in solution, and hClpX must exert an allosteric effect on hClpP to promote a conformation that stabilizes the tetradecamer. These data suggest that hClpX can regulate the appearance of hClpP peptidase activity in mitochondria and might affect the nature of the degradation products released during ATP-dependent proteolytic cycles.

Received for publication, July 5, 2005 , and in revised form, August 12, 2005.

^* This research was supported by the Intramural Research Program of the National Institutes of Health, NCI, Center for Cancer Research, and NHLBI. 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: Marine Biotechnology Research Centre, KORDI, P. O. Box 29, Ansan, 425-600, Korea.

² Present address: 1200 Main Street West Health Sciences Centre, Rm. 4H24 Department of Biochemistry and Biomedical Sciences, McMaster University Hamilton, ON Canada L8N3Z5.

³ To whom correspondence should be addressed: Laboratory of Cell Biology, National Cancer Institute, Bldg. 37 Rm. 2128, 37 Convent Drive, Bethesda, MD 20892-4255. Tel.: 301-496-7961; Fax: 301-480-0450; E-mail: mmaurizi{at}helix.nih.gov.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				A. Rudella, G. Friso, J. M. Alonso, J. R. Ecker, and K. J. van Wijk Downregulation of ClpR2 Leads to Reduced Accumulation of the ClpPRS Protease Complex and Defects in Chloroplast Biogenesis in Arabidopsis PLANT CELL, July 1, 2006; 18(7): 1704 - 1721. [Abstract] [Full Text] [PDF]