Two flexible loops in subtilisin-like thermophilic protease, thermicin, from Thermoanaerobacter yonseiensis

Jin Jang Hyeung, Chang Hun Lee, Weontae Lee, Sam Kim Yu

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10 Citations (Scopus)


A gene that encodes a thermostable protease, coined thermicin, has been isolated from Thermoanaerobacter yonseiensis that is expressed and characterized in E. coli. In order to elucidate the molecular characteristics on thermostability of the enzyme, molecular modeling and mutagenesis technology were applied. In the modeling structure, the structural core, including the active site, was well conserved; whereas, the two loop regions were unique when compared to thermitase. The mutant enzyme with the small loop deleted (D190-I196), based on modeling structural information, showed identical enzyme activity. However, when the large loop was deleted (P233-P244), a little lower Km and even a lower kcat was found. This indicates that the large loop could influence catalytic activity. However, the unfolding temperature (Tm), which was determined by a differential-scanning calorimetry for the mutant enzyme deleted the small loop, was 96°C. This is 14°C lower than that for the parent thermicin. These results suggest that the small loop may play a role in maintaining the proper folding of the enzyme at high temperatures, whereas the large loop might be related to catalysis.

Original languageEnglish
Pages (from-to)498-507
Number of pages10
JournalJournal of biochemistry and molecular biology
Issue number5
Publication statusPublished - 2002 Sept

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology


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