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

J. Biol. Chem., Vol. 280, Issue 26, 24301-24307, July 1, 2005

This Article Full Text Full Text (PDF) All Versions of this Article: 280/26/24301    most recent M502483200v1 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 Nogaj, L. A. Articles by Beale, S. I. Search for Related Content PubMed PubMed Citation Articles by Nogaj, L. A. Articles by Beale, S. I. Social Bookmarking                      What's this?

Physical and Kinetic Interactions between Glutamyl-tRNA Reductase and Glutamate-1-semialdehyde Aminotransferase of Chlamydomonas reinhardtii^*

Luiza A. Nogaj and Samuel I. Beale

From the Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912

In plants, algae, and most bacteria, the heme and chlorophyll precursor 5-aminolevulinic acid (ALA) is formed from glutamate in a three-step process. First, glutamate is ligated to its cognate tRNA by glutamyl-tRNA synthetase. Activated glutamate is then converted to a glutamate 1-semialdehyde (GSA) by glutamyl-tRNA reductase (GTR) in an NADPH-dependent reaction. Subsequently, GSA is rearranged to ALA by glutamate-1-semialdehyde aminotransferase (GSAT). The intermediate GSA is highly unstable under physiological conditions. We have used purified recombinant GTR and GSAT from the unicellular alga Chlamydomonas reinhardtii to show that GTR and GSAT form a physical and functional complex that allows channeling of GSA between the enzymes. Co-immunoprecipitation and sucrose gradient ultracentrifugation results indicate that recombinant GTR and GSAT enzymes specifically interact. In vivo cross-linking results support the in vitro results and demonstrate that GTR and GSAT are components of a high molecular mass complex in C. reinhardtii cells. In a coupled enzyme assay containing GTR and wild-type GSAT, addition of inactive mutant GSAT inhibited ALA formation from glutamyl-tRNA. Mutant GSAT did not inhibit ALA formation from GSA by wild-type GSAT. These results suggest that there is competition between wild-type and mutant GSAT for binding to GTR and channeling GSA from GTR to GSAT. Further evidence supporting kinetic interaction of GTR and GSAT is the observation that both wild-type and mutant GSAT stimulate glutamyl-tRNA-dependent NADPH oxidation by GTR.

Received for publication, March 7, 2005 , and in revised form, April 28, 2005.

^* This work was supported by National Science Foundation Grant MCB-9808578 (to S. I. B.). 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 should be addressed: Biomed. Box G-J4, Brown University, Providence, RI 02912. Tel.: 401-863-3129; Fax: 401-863-1182; E-mail: sib{at}brown.edu.

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

This article has been cited by other articles:

				A. Masoumi, I. U. Heinemann, M. Rohde, M. Koch, M. Jahn, and D. Jahn Complex formation between protoporphyrinogen IX oxidase and ferrochelatase during haem biosynthesis in Thermosynechococcus elongatus Microbiology, December 1, 2008; 154(12): 3707 - 3714. [Abstract] [Full Text] [PDF]

				W. Y. Bang, I. S. Jeong, D. W. Kim, C. H. Im, C. Ji, S. M. Hwang, S. W. Kim, Y. S. Son, J. Jeong, T. Shiina, et al. Role of Arabidopsis CHL27 Protein for Photosynthesis, Chloroplast Development and Gene Expression Profiling Plant Cell Physiol., September 1, 2008; 49(9): 1350 - 1363. [Abstract] [Full Text] [PDF]

				L. A. Nogaj, A. Srivastava, R. van Lis, and S. I. Beale Cellular Levels of Glutamyl-tRNA Reductase and Glutamate-1-Semialdehyde Aminotransferase Do Not Control Chlorophyll Synthesis in Chlamydomonas reinhardtii Plant Physiology, September 1, 2005; 139(1): 389 - 396. [Abstract] [Full Text] [PDF]