title: The EM structure of human DNA polymerase gamma reveals a localized contact between the catalytic and accessory subunits.
abstract: We used electron microscopy to examine the structure of human DNA pol gamma, the heterotrimeric mtDNA replicase implicated in certain mitochondrial diseases and aging models. Separate analysis of negatively stained preparations of the catalytic subunit, pol gammaA, and of the holoenzyme including a dimeric accessory factor, pol gammaB(2), permitted unambiguous identification of the position of the accessory factor within the holoenzyme. The model explains protection of a partial chymotryptic cleavage site after residue L(549) of pol gammaA upon binding of the accessory subunit. This interaction region is near residue 467 of pol gammaA, where a disease-related mutation has been reported to impair binding of the B subunit. One pol gammaB subunit dominates contacts with the catalytic subunit, while the second B subunit is largely exposed to solvent. A model for pol gamma is discussed that considers the effects of known mutations in the accessory subunit and the interaction of the enzyme with DNA.
authors.affiliation: Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Yakubovskaya
authors.forename: Mark
authors.initials: M
authors.lastname: Lukin
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Chen
authors.forename: John
authors.initials: J
authors.lastname: Berriman
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Wall
authors.forename: Ryuji
authors.initials: R
authors.lastname: Kobayashi
authors.forename: Caroline
authors.initials: C
authors.lastname: Kisker
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Bogenhagen
mesh_terms: D000375:Aging / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D002918:Chymotrypsin / Q000737:chemistry; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000648:ultrastructure; D006801:Humans; D046529:Microscopy, Electron, Transmission; D028361:Mitochondrial Diseases / Q000201:enzymology / Q000235:genetics; D008954:Models, Biological; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
chemical_list: D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D002918:Chymotrypsin