Intersubunit disulfide interactions play a critical role in maintaining the thermostability of glucose-6-phosphate dehydrogenase from the hyperthermophilic bacterium Aquifex aeolicus

Manjula Nakka, Ramesh B. Iyer, Leonidas G. Bachas

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Proteins from thermophilic microorganisms are stabilized by various mechanisms to preserve their native folded states at higher temperatures. A thermostable glucose-6-phosphate dehydrogenase (tG6PDH) from the hyperthermophilic bacterium Aquifex aeolicus was expressed as a recombinant protein in Escherichia coli. The A. aeolicus G6PDH is a homodimer exhibiting remarkable thermostability (t 1/2=24 hr at 90°C). Based on homology modeling and upon comparison of its structure with human G6PDH, it was predicted that cysteine 184 of one subunit could form a disulfide bond with cysteine 352 of the other subunit resulting in reinforced intersubunit interactions that hold the dimer together. Site-directed mutagenesis was performed on tG6PDH to convert C184 and C352 to serines. The tG6PDH double mutant exhibited a dramatic decrease in the half-life from 24 hr to 3 hr at 90°C. The same decrease in half-life was also found when either C184 or C352 was mutated to serine. The result indicates that C184 and C352 may play a crucial role in strengthening the dimer interface through disulfide bond formation, thereby contributing to the thermal stability of the enzyme.

Original languageEnglish (US)
Pages (from-to)17-21
Number of pages5
JournalProtein Journal
Volume25
Issue number1
DOIs
StatePublished - Jan 1 2006
Externally publishedYes

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Keywords

  • Aquifex aeolicus G6PDH
  • Disulfide bond
  • Homology modeling
  • Site-directed mutagenesis
  • Subunit interactions

ASJC Scopus subject areas

  • Analytical Chemistry
  • Bioengineering
  • Biochemistry
  • Organic Chemistry

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