Crystal structure and deletion analysis show that the accessory subunit of mammalian DNA polymerase gamma, Pol gamma B, functions as a homodimer

Mol Cell. 2001 Jan;7(1):43-54. doi: 10.1016/s1097-2765(01)00153-8.


Polymerase gamma, which replicates and repairs mitochondrial DNA, requires the Pol gamma B subunit for processivity. We determined the crystal structure of mouse Pol gamma B, a core component of the mitochondrial replication machinery. Pol gamma B shows high similarity to glycyl-tRNA synthetase and dimerizes through an unusual intermolecular four-helix bundle. A human Pol gamma B mutant lacking the four-helix bundle failed to dimerize in solution or to stimulate the catalytic subunit Pol gamma A, but retained the ability to bind with Pol gamma A to a primer-template construct, indicating that the functional holoenzyme contains two Pol gamma B molecules. Other mutants retained stimulatory activity but lost the ability to bind folded ssDNA. These results suggest that the Pol gamma B dimer contains distinct sites for Pol gamma A binding, dimerization, and DNA binding.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites / physiology
  • Crystallography
  • DNA Polymerase gamma
  • DNA Replication / physiology*
  • DNA, Single-Stranded / metabolism
  • DNA-Directed DNA Polymerase / chemistry*
  • DNA-Directed DNA Polymerase / genetics*
  • DNA-Directed DNA Polymerase / metabolism
  • Dimerization
  • Gene Deletion*
  • Glycine-tRNA Ligase / chemistry
  • Glycine-tRNA Ligase / genetics
  • Humans
  • Mammals
  • Mice
  • Mitochondria / genetics
  • Molecular Sequence Data
  • Protein Folding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Surface Properties
  • Water / chemistry


  • DNA, Single-Stranded
  • Water
  • DNA Polymerase gamma
  • DNA-Directed DNA Polymerase
  • Glycine-tRNA Ligase

Associated data

  • PDB/1G5H