Journal Article

Thermostability of ancestral mutants of <i>Caldococcus noboribetus</i> isocitrate dehydrogenase

Hisako Iwabata, Keiko Watanabe, Takatoshi Ohkuri, Shin-ichi Yokobori and Akihiko Yamagishi

in FEMS Microbiology Letters

Volume 243, issue 2, pages 393-398
Published in print February 2005 |
Published online January 2006 | e-ISSN: 1574-6968 | DOI:

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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.

Keywords: Common ancestor; Hyperthermophile; Isocitrate dehydrogenase; Protein thermostability; Caldococcus noboribetus; Commonote; 3-Isopropylmalate dehydrogenase

Journal Article.  3009 words.  Illustrated.

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