Structural insight into the reaction mechanism and evolution of cytokinin biosynthesis

Hajime Sugawara, Nanae Ueda, Mikiko Kojima, Nobue Makita, Tomoyuki Yamaya, Hitoshi Sakakibara

    Research output: Contribution to journalArticlepeer-review

    23 Citations (Scopus)


    The phytohormone cytokinin regulates plant growth and development. This hormone is also synthesized by some phytopathogenic bacteria, such as Agrobacterium tumefaciens, and is as a key factor in the formation of plant tumors. The rate-limiting step of cytokinin biosynthesis is catalyzed by adenosine phosphate-isopentenyltransferase (IPT). Agrobacterium IPT has a unique substrate specificity that enables it to increase trans-zeatin production by recruiting a metabolic intermediate of the host plant's biosynthetic pathway. Here, we show the crystal structures of Tzs, an IPT from A. tumefaciens, complexed with AMP and a prenyl-donor analogue, dimethylallyl S-thiodiphosphate. The structures reveal that the carbon-nitrogen-based prenylation proceeds by the SN2-reaction mechanism. Site-directed mutagenesis was used to determine the amino acid residues, Asp-173 and His-214, which are responsible for differences in prenyl-donor substrate specificity between plant and bacterial IPTs. IPT and the p loop-containing nucleoside triphosphate hydrolases likely evolved from a common ancestral protein. Despite structural similarities, IPT has evolved a distinct role in which the p loop transfers a prenyl moiety in cytokinin biosynthesis.

    Original languageEnglish
    Pages (from-to)2734-2739
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Issue number7
    Publication statusPublished - 2008 Feb 19


    • Agrobacterium tumefaciens
    • Crystal structure
    • Isopentenyltransferase
    • P loop-containing nucleoside triphosphate hydrolases
    • Trans-zeatin

    ASJC Scopus subject areas

    • General

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