Refined 2.5 Å structure of murine adenosine deaminase at pH 6.0

Andrew J. Sharff, David K. Wilson, Zengyi Chang, Florante A. Quiocho

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65 Scopus citations


The X-ray structure of murine adenosine deaminase complexed with the transition-state analogue 6-hydroxyl-1,6-dihydropurine ribonucleoside has been determined from a single crystal grown at pH 4.2 and transferred to mother liquor of increasing pH up to a final pH of 6.0 prior to data collection. The structure has been refined to 2.5 Å to a final crystallographic R-factor of 20 % using phases from the previously refined 2.4 Å structure at pH 4.2. Kinetic measurements show that the enzyme is only 20% active at pH 4.2 whereas it is fully active between pH 6.0 and pH 8.5. The refined structures at either pH are essentially the same. Consideration of the pKa values of the key catalytic residues and the mechanism proposed on the basis of the structure suggests that the ionization state of these residues is largely responsible for the pH dependence on activity.

Original languageEnglish (US)
Pages (from-to)917-921
Number of pages5
JournalJournal of Molecular Biology
Issue number4
StatePublished - May 20 1992
Externally publishedYes


  • adenosine deaminase
  • conformational change
  • ionization states
  • pH
  • X-ray crystal structure

ASJC Scopus subject areas

  • Virology


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