Purification and functional characterization of human mitochondrial DNA polymerase gamma harboring disease mutations

Methods. 2010 Aug;51(4):379-84. doi: 10.1016/j.ymeth.2010.02.015. Epub 2010 Feb 20.


More than 150 different point mutations in POLG, the gene encoding the human mitochondrial DNA polymerase gamma (pol gamma), cause a broad spectrum of childhood and adult onset diseases like Alpers syndrome, ataxia-neuropathy syndrome and progressive external ophthalmoplegia. These disease mutations can affect the pol gamma enzyme's properties in numerous ways, thus potentially influencing the severity of the disease. Hence, a detailed characterization of disease mutants will greatly assist researchers and clinicians to develop a clear understanding of the functional defects caused by these mutant enzymes. Experimental approaches for characterizing the wild-type (WT) and mutant pol gamma enzymes are extensively described in this manuscript. The methods start with construction and purification of the recombinant wild-type and mutant forms of pol gamma protein, followed by assays to determine its structural integrity and thermal stability. Next, the biochemical characterization of these enzymes is described in detail, which includes measuring the purified enzyme's catalytic activity, its steady-state kinetic parameters and DNA binding activity, and determining the physical and functional interaction of these pol gamma proteins with the p55 accessory subunit.

Publication types

  • Research Support, N.I.H., Intramural
  • Review

MeSH terms

  • Base Sequence
  • DNA Polymerase gamma
  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / metabolism
  • DNA-Directed DNA Polymerase / genetics*
  • DNA-Directed DNA Polymerase / isolation & purification*
  • DNA-Directed DNA Polymerase / metabolism
  • Enzyme Stability
  • Humans
  • In Vitro Techniques
  • Kinetics
  • Mutagenesis, Site-Directed
  • Mutant Proteins / genetics
  • Mutant Proteins / isolation & purification
  • Mutant Proteins / metabolism
  • Mutation*
  • Protein Subunits
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism


  • DNA, Mitochondrial
  • Mutant Proteins
  • Protein Subunits
  • Recombinant Proteins
  • DNA Polymerase gamma
  • DNA-Directed DNA Polymerase
  • POLG protein, human