This Article Full Text Full Text (PDF) All Versions of this Article: 141/3/1120    most recent pp.106.082859v1 Alert me when this article is cited Alert me if a correction is posted 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 CrossRef Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Awai, K. Articles by Ohta, H. Search for Related Content PubMed PubMed Citation Articles by Awai, K. Articles by Ohta, H. Agricola Articles by Awai, K. Articles by Ohta, H.

BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Comparative Genomic Analysis Revealed a Gene for Monoglucosyldiacylglycerol Synthase, an Enzyme for Photosynthetic Membrane Lipid Synthesis in Cyanobacteria¹

Graduate School for Bioscience and Biotechnology (K.A., T. Kakimoto, C.A., Y.N., K.T., H.O.) and Research Center for the Evolving Earth and Planets (K.T., H.O.), Tokyo Institute of Technology, Midori-ku, Yokohama 226–8501, Japan; Kazusa DNA Research Institute, Kisarazu, Chiba 292–0818, Japan (T. Kaneko); and Graduate School of Arts and Sciences, University of Tokyo, Komaba, Tokyo 153–8902, Japan (H.W.)

Cyanobacteria have a thylakoid lipid composition very similar to that of plant chloroplasts, yet cyanobacteria are proposed to synthesize monogalactosyldiacylglycerol (MGDG), a major membrane polar lipid in photosynthetic membranes, by a different pathway. In addition, plant MGDG synthase has been cloned, but no ortholog has been reported in cyanobacterial genomes. We report here identification of the gene for monoglucosyldiacylglycerol (MGlcDG) synthase, which catalyzes the first step of galactolipid synthesis in cyanobacteria. Using comparative genomic analysis, candidates for the gene were selected based on the criteria that the enzyme activity is conserved between two species of cyanobacteria (unicellular [Synechocystis sp. PCC 6803] and filamentous [Anabaena sp. PCC 7120]), and we assumed three characteristics of the enzyme; namely, it harbors a glycosyltransferase motif, falls into a category of genes with unknown function, and shares significant similarity in amino acid sequence between these two cyanobacteria. By a motif search of all genes of Synechocystis, BLAST searches, and similarity searches between these two cyanobacteria, we identified four candidates for the enzyme that have all the characteristics we predicted. When expressed in Escherichia coli, one of the Synechocystis candidate proteins showed MGlcDG synthase activity in a UDP-glucose-dependent manner. The ortholog in Anabaena also showed the same activity. The enzyme was predicted to require a divalent cation for its activity, and this was confirmed by biochemical analysis. The MGlcDG synthase and the plant MGDG synthase shared low similarity, supporting the presumption that cyanobacteria and plants utilize different pathways to synthesize MGDG.

² Present address: Graduate School of Science and Engineering, Saitama University, Saitama 338–8570, Japan.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Koichiro Awai (awai{at}molbiol.saitama-u.ac.jp).

Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.106.082859.

^* Corresponding author; e-mail awai{at}molbiol.saitama-u.ac.jp; fax 81–48–858–3384.

Received May 3, 2006; returned for revision May 9, 2006; accepted May 9, 2006.

This article has been cited by other articles:

				C. Botte, N. Saidani, R. Mondragon, M. Mondragon, G. Isaac, E. Mui, R. McLeod, J.-F. Dubremetz, H. Vial, R. Welti, et al. Subcellular localization and dynamics of a digalactolipid-like epitope in Toxoplasma gondii J. Lipid Res., April 1, 2008; 49(4): 746 - 762. [Abstract] [Full Text] [PDF]

				K. Awai, H. Watanabe, C. Benning, and I. Nishida Digalactosyldiacylglycerol is Required for Better Photosynthetic Growth of Synechocystis sp. PCC6803 Under Phosphate Limitation Plant Cell Physiol., November 1, 2007; 48(11): 1517 - 1523. [Abstract] [Full Text] [PDF]

				N. Sato and T. Moriyama Genomic and Biochemical Analysis of Lipid Biosynthesis in the Unicellular Rhodophyte Cyanidioschyzon merolae: Lack of a Plastidic Desaturation Pathway Results in the Coupled Pathway of Galactolipid Synthesis Eukaryot. Cell, June 1, 2007; 6(6): 1006 - 1017. [Abstract] [Full Text] [PDF]