Crystal structure and deletion analysis show that the accessory subunit of mammalian DNA polymerase gamma, Pol gamma B, functions as a homodimer.
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.
Carrodeguas
J A
JA
Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA.
Theis
K
K
Bogenhagen
D F
DF
Kisker
C
C
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D003461:Crystallography; D000074002:DNA Polymerase gamma; D004261:DNA Replication / Q000502:physiology*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D019281:Dimerization; D017353:Gene Deletion; D006032:Glycine-tRNA Ligase / Q000737:chemistry / Q000235:genetics; D006801:Humans; D008322:Mammals; D051379:Mice; D008928:Mitochondria / Q000235:genetics; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D004277:DNA, Single-Stranded; D014867:Water; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D006032:Glycine-tRNA Ligase