Small angle X-ray scattering studies of mitochondrial glutaminase C reveal extended flexible regions, and link oligomeric state with enzyme activity

PLoS One. 2013 Sep 30;8(9):e74783. doi: 10.1371/journal.pone.0074783. eCollection 2013.


Glutaminase C is a key metabolic enzyme, which is unregulated in many cancer systems and believed to play a central role in the Warburg effect, whereby cancer cells undergo changes to an altered metabolic profile. A long-standing hypothesis links enzymatic activity to the protein oligomeric state, hence the study of the solution behavior in general and the oligomer state in particular of glutaminase C is important for the understanding of the mechanism of protein activation and inhibition. In this report, this is extensively investigated in correlation to enzyme concentration or phosphate level, using a high-throughput microfluidic-mixing chip for the SAXS data collection, and we confirm that the oligomeric state correlates with activity. The in-depth solution behavior analysis further reveals the structural behavior of flexible regions of the protein in the dimeric, tetrameric and octameric state and investigates the C-terminal influence on the enzyme solution behavior. Our data enable SAXS-based rigid body modeling of the full-length tetramer states, thereby presenting the first ever experimentally derived structural model of mitochondrial glutaminase C including the N- and C-termini of the enzyme.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Area Under Curve
  • Glutaminase / chemistry*
  • Glutaminase / genetics
  • Humans
  • Microfluidics
  • Mitochondrial Proteins / chemistry*
  • Mitochondrial Proteins / genetics
  • Models, Molecular*
  • Oligonucleotides / genetics
  • Protein Conformation*
  • Scattering, Small Angle


  • Mitochondrial Proteins
  • Oligonucleotides
  • Glutaminase