Crystal structures of 3-isopropylmalate dehydrogenases with mutations at the C-terminus: Crystallographic analyses of structure-stability relationships

Zeily Nurachman, Satoshi Akanuma, Takao Sato, Tairo Oshima, Nobuo Tanaka

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10 Citations (Scopus)


Thermal stability of the Thermus thermophilus isopropylmalate dehydrogenase enzyme was substantially lost upon the deletion of three residues from the C-terminus. However, the stability was partly recovered by the addition of two, four and seven amino acid residues (called HD177, HD708 and HD711, respectively) to the C-terminal region of the truncated enzyme. Three structures of these mutant enzymes were determined by an X-ray diffraction method. All protein crystals belong to space group P21 and their structures were solved by a standard molecular replacement method where the original dimer structure of the A172L mutant was used as a search model. Thermal stability of these mutant enzymes is discussed based on the 3D structure with special attention to the width of the active-site groove and the minor groove, distortion of β-sheet pillar structure and size of cavity in the domain-domain interface around the C-terminus. Our previous studies revealed that the thermal stability of isopropylmalate dehydrogenase increases when the active-site cleft is closed (the closed form). In the present study it is shown that the active-site cleft can be regulated by open-close movement of the minor groove located at the opposite side to the active-site groove on the same subunit, through a paperclip-like motion.

Original languageEnglish
Pages (from-to)253-258
Number of pages6
JournalProtein Engineering
Issue number4
Publication statusPublished - 2000 May 24



  • 3-Isopropylmalate dehydrogenase
  • Closed conformation
  • Minor groove
  • Modified C-terminus
  • Paperclip motion

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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