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

J. Biol. Chem., Vol. 282, Issue 18, 13845-13853, May 4, 2007

This Article Full Text Full Text (PDF) All Versions of this Article: 282/18/13845    most recent M608385200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted 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 Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Yeh, Y.-H. Articles by Hsiao, C.-D. Search for Related Content PubMed PubMed Citation Articles by Yeh, Y.-H. Articles by Hsiao, C.-D. Social Bookmarking                      What's this?

Dimerization Is Important for the GTPase Activity of Chloroplast Translocon Components atToc33 and psToc159^*

Yi-Hung Yeh, Muppuru M. Kesavulu, Hsou-min Li, Shu-Zon Wu, Yuh-Ju Sun, Emadeldin H. E. Konozy, and Chwan-Deng Hsiao¹

From the Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan 115, Republic of China and the Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan 300, Republic of China

Arabidopsis Toc33 (atToc33) is a GTPase and a member of the Toc (translocon at the outer-envelope membrane of chloroplasts) complex that associates with precursor proteins during protein import into chloroplasts. By inference from the crystal structure of psToc34, a homologue in pea, the arginine at residue 130 (Arg¹³⁰) has been implicated in the formation of the atToc33 dimer and in intermolecular GTPase activation within the dimer. Here we report the crystal structure at 3.2-Å resolution of an atToc33 mutant, atToc33(R130A), in which Arg¹³⁰ was mutated to alanine. Both in solution and in crystals, atToc33(R130A) was present in its monomeric form. In contrast, both wild-type atToc33 and another pea Toc GTPase homologue, pea Toc159 (psToc159), were able to form dimers in solution. Dimeric atToc33 and psToc159 had significantly higher GTPase activity than monomeric atToc33, psToc159, and atToc33(R130A). Molecular modeling using the structures of psToc34 and atToc33(R130A) suggests that, in an architectural dimer of atToc33, Arg¹³⁰ from one monomer interacts with the -phosphate of GDP and several other amino acids of the other monomer. These results indicate that Arg¹³⁰ is critical for dimer formation, which is itself important for GTPase activity. Activation of GTPase activity by dimer formation is likely to be a critical regulatory step in protein import into chloroplasts.

Received for publication, August 31, 2006 , and in revised form, February 8, 2007.

The atomic coordinates and structure factors (code 2J3E) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

^* This work was supported in part by research grants from Academia Sinica and the National Science Council (NSC94-2311-B-001-072 (to C.-D. H.) and NSC95-2321-B-001-004 (to H.-m. L.), Taiwan, Republic of China. 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 To whom correspondence should be addressed. Tel.: 886-2-2788-2743; Fax: 886-2-2782-6085; E-mail: hsiao{at}gate.sinica.edu.tw.

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

This article has been cited by other articles:

				B. Agne, S. Infanger, F. Wang, V. Hofstetter, G. Rahim, M. Martin, D. W. Lee, I. Hwang, D. Schnell, and F. Kessler A Toc159 Import Receptor Mutant, Defective in Hydrolysis of GTP, Supports Preprotein Import into Chloroplasts J. Biol. Chem., March 27, 2009; 284(13): 8670 - 8679. [Abstract] [Full Text] [PDF]

				G. Rahim, S. Bischof, F. Kessler, and B. Agne In vivo interaction between atToc33 and atToc159 GTP-binding domains demonstrated in a plant split-ubiquitin system J. Exp. Bot., January 1, 2009; 60(1): 257 - 267. [Abstract] [Full Text] [PDF]

				T. Bionda, P. Koenig, M. Oreb, I. Tews, and E. Schleiff pH Sensitivity of the GTPase Toc33 as a Regulatory Circuit for Protein Translocation into Chloroplasts Plant Cell Physiol., December 1, 2008; 49(12): 1917 - 1921. [Abstract] [Full Text] [PDF]

				P. Koenig, M. Oreb, K. Rippe, C. Muhle-Goll, I. Sinning, E. Schleiff, and I. Tews On the Significance of Toc-GTPase Homodimers J. Biol. Chem., August 22, 2008; 283(34): 23104 - 23112. [Abstract] [Full Text] [PDF]

				M. Kalanon and G. I. McFadden The Chloroplast Protein Translocation Complexes of Chlamydomonas reinhardtii: A Bioinformatic Comparison of Toc and Tic Components in Plants, Green Algae and Red Algae Genetics, May 1, 2008; 179(1): 95 - 112. [Abstract] [Full Text] [PDF]