Thermostability of ancestral mutants of Caldococcus noboribetus isocitrate dehydrogenase

  • Iwabata H
  • Watanabe K
  • Ohkuri T
 et al. 
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We constructed mutant genes of Caldococcus noboribetus isocitrate dehydrogenase containing ancestral amino acid residues that were inferred using the maximal likelihood method and a composite phylogenetic tree of isocitrate dehydrogenase and 3-isopropylmalate dehydrogenase. The mutant genes were expressed in Escherichia coli and the protein products purified. Thermostabilities, reported as the half-inactivation temperatures, for the purified enzymes were determined and compared with that of the wild-type enzyme. Four of the five mutant enzymes have greater thermal stabilities than wild-type isocitrate dehydrogenase. The results are compatible with the hyperthermophilic universal ancestor (commonote) hypothesis. Incorporation of ancestral residues into a modern-day protein sequence can be used to improve protein thermostability. © 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

Author-supplied keywords

  • 3-Isopropylmalate dehydrogenase
  • Caldococcus noboribetus
  • Common ancestor
  • Commonote
  • Hyperthermophile
  • Isocitrate dehydrogenase
  • Protein thermostability

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  • Hisako Iwabata

  • Keiko Watanabe

  • Takatoshi Ohkuri

  • Shin Ichi Yokobori

  • Akihiko Yamagishi

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