Allosteric regulation and substrate activation in cytosolic nucleotidase II from Legionella pneumophila

Bharath Srinivasan, Farhad Forouhar, Arpit Shukla, Chethana Sampangi, Sonia Kulkarni, Mariam Abashidze, Jayaraman Seetharaman, Scott Lew, Lei Mao, Thomas B. Acton, Rong Xiao, John K. Everett, Gaetano T. Montelione, Liang Tong, Hemalatha Balaram

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Cytosolic nucleotidase II (cN-II) from Legionella pneumophila (Lp) catalyzes the hydrolysis of GMP and dGMP displaying sigmoidal curves, whereas catalysis of IMP hydrolysis displayed a biphasic curve in the initial rate versus substrate concentration plots. Allosteric modulators of mammalian cN-II did not activate LpcN-II although GTP, GDP and the substrate GMP were specific activators. Crystal structures of the tetrameric LpcN-II revealed an activator-binding site at the dimer interface. A double mutation in this allosteric-binding site abolished activation, confirming the structural observations. The substrate GMP acting as an activator, partitioning between the allosteric and active site, is the basis for the sigmoidicity of the initial velocity versus GMP concentration plot. The LpcN-II tetramer showed differences in subunit organization upon activator binding that are absent in the activator-bound human cN-II structure. This is the first observation of a structural change induced by activator binding in cN-II that may be the molecular mechanism for enzyme activation.

Original languageEnglish (US)
Pages (from-to)1613-1628
Number of pages16
JournalFEBS Journal
Issue number6
StatePublished - 2014

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


  • 5′-nucleotidase
  • GMP-complexed LpcN-II structure
  • allostery
  • heterotropic activation
  • substrate activation

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