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Title: MEMBERS OF THE ARABIDOPSIS FAE1-LIKE 3-KETOSYNTHASE GENE FAMILY SUBSTITUTE FOR THE ELOP PROTEINS OF SACCHAROMYCES CEREVISIAE

Author
item PAUL, SHILPI - UNIV OF HEALTH SCIENCES
item GABLE, KENNETH - UNIV OF HEALTH SCIENCES
item BEAUDOIN, FREDERIC - ROTHAMSTED RESEARCH
item Cahoon, Edgar
item JAWORSKI, JAN - D DANFORTH PLT SCI CTR
item NAPIER, JOHNATHAN - ROTHAMSTED RESEARCH
item DUNN, TERESA - UNIV OF HEALTH SCIENCES

Submitted to: Journal of Biological Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2006
Publication Date: 4/7/2006
Citation: Paul, S., Gable, K., Beaudoin, F., Cahoon, E.B., Jaworski, J., Napier, J.A., Dunn, T.M. 2006. Members of the Arabidopsis FAE1-like 3-ketosynthase gene family substitute for the elop proteins of saccharomyces cerevisiae. Journal of Biological Chemistry. 281:9018-9029.

Interpretive Summary: Fatty acids with very-long carbon chains are components of the surface waxes of plant leaves and are also found in vegetable oils of certain crop species. How the enzymes associated with the elongation of fatty acids in plants and other organisms are functionally organized is largely unknown. A detailed biochemical understanding of fatty acid elongation may be important for engineering increased wax content for drought resistance and for generating higher value vegetable oils. In this study, a yeast model system was used to show that two structurally unrelated classes of enzymes are able to substitute for one another to catalyze the first reaction in fatty acid elongation. We also show that these enzymes are able to physically interact with other enzymes involved in fatty acid elongation to form an active complex. The results from these studies will be useful to biochemists and geneticists who are attempting to improve the stress resistance of plants and to enhance the value of existing oilseed crops such as soybean. This research will contribute to improvements in the productivity and value of crop plants for U.S. farmers.

Technical Abstract: Several 3-ketoacyl-CoA synthases have been studied including the soluble fatty acid synthases, those involved in polyketide synthesis, and the FAE1-like 3-ketoacyl-CoA synthases. All of these condensing enzymes have a common ancestor and an enzymatic mechanism that involves a catalytic triad consisting of Cys, His and His/Asn. In contrast to the FAE1-like family of enzymes that mediate plant microsomal fatty acid elongation, the condensation step of elongation in animals and in fungi appears to be mediated by the Elop homologs. Curiously these proteins bear no resemblance to the well-characterized 3-keto-synthases. There are three ELO genes in yeast that encode the homologous Elo1p, Elo2p and Elo3p proteins. Elo2p and Elo3p are required for synthesis of the very long chain fatty acids, and mutants lacking both Elo2p and Elo3p are not viable confirming that the very long chain fatty acids are essential for cellular functions. In this study we show that heterologous expression of several Arabidopsis FAE1-like genes rescues the lethality of an elo2/elo3 yeast mutant. We further demonstrate that Fae1p acts in conjunction with the 3-keto and trans-2,3,-enoyl reductases of the elongase system. These studies indicate that even though the plant-specific Fae1p family of condensing enzymes evolved independently of the Elop family of condensing enzymes, they utilize the same reductases and presumably dehydratase that the Elop proteins rely upon.