Cryogenic x-ray crystal structure analysis for the complex of scytalone dehydratase of a rice blast fungus and its tight-binding inhibitor, carpropamid: The structural basis of tight-binding inhibition

Masayoshi Nakasako, Takayuki Motoyama, Yoshio Kurahashi, Isamu Yamaguchi

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Scytalone dehydratase is a member of the group of enzymes involved in fungal melanin biosynthesis in a phytopathogenic fungus, Pyricularia oryzae, which causes rice blast disease. Carpropamid tight-binding inhibitor of the enzyme. To clarify the structural basis for tight-binding inhibition, the crystal structure of the enzyme complexed with carpropamid was analyzed using diffraction data collected at 100 K. The structural model was refined to a crystallographic R-factor of 0.180 against reflections up to a resolution of 2.1 Å. Carpropamid was bound in a hydrophobic cavity of the enzyme. Three types of interactions appeared to contribute to the binding. (i) A hydrogen bond was formed between a chloride atom in the dichloromethylethylcyclopropane ring of carpropamid and Ash-131 of the enzyme. (ii) The (chlorophenyl)ethyl group of carpropamid built strong contacts with Val-75, and this group further formed a cluster of aromatic rings together with four aromatic residues in the enzyme (Tyr-50, Phe-53, Phe-158, and Phe-162). (iii) Two hydration water molecules bound to the carboxamide group of carpropamid, and they were further hydrogen-bonded to Tyr-30, Tyr-50, His-85, and His-110. As a result of interactions between carpropamid and the phenylalanine residues (Phe-158 and Phe-162) in the C- terminal region of the enzyme, the C-terminal region completely covered the inhibitor, ensuring its localization in the cavity.

Original languageEnglish
Pages (from-to)9931-9939
Number of pages9
Issue number28
Publication statusPublished - 1998 Jul 14
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry

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