Journal of Molecular Evolution

, Volume 48, Issue 6, pp 756–769 | Cite as

DNA Polymerase C of the Thermophilic Bacterium Thermus aquaticus: Classification and Phylogenetic Analysis of the Family C DNA Polymerases

  • Yi-Ping  Huang
  • Junetsu  Ito

Abstract.

Bacterial family C DNA polymerases (DNA pol IIIs), the major chromosomal replicative enzymes, have been provisionally classified based on primary sequences and domain structures into three classes: class I (Escherichia coli DNA pol C-type), class II (Bacillus subtilis DNA pol C-type), and class III (cyanobacterial DNA pol C-type), respectively. We have sequenced the structural gene encoding the DNA pol C catalytic subunit of the thermophilic bacterium Thermus aquaticus. This gene, designated the Taq DNA pol C gene, contains a 3660-bp open reading frame which specifies a polypeptide of molecular weight of 137,388 daltons. Comparative sequence analyses revealed that Taq DNA pol C is a class I family C DNA polymerase. The Taq DNA pol C is most closely related to the Deinococcus radiodurans DNA pol C. Although a phylogenetic tree based on the class I family C DNA pols is still in the provisional stage, some important conclusion can be drawn. First, the high-G+C and the low-G+C Gram-positive bacteria are not monophyletic. Second, the low-G+C Gram-positive bacteria contain multigenes of family C DNA pols (classes I and II). Third, the cyanobacterial family C DNA pol, classified as class III because it is encoded by a split gene, forms a group with the high-G+C Gram-positive bacteria.

Key words: Family C DNA polymerases —Thermus aquaticus— Phylogeny — Classification of the family C DNA polymerases 

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Copyright information

© Springer-Verlag New York Inc. 1999

Authors and Affiliations

  • Yi-Ping  Huang
    • 1
  • Junetsu  Ito
    • 1
  1. 1.Department of Microbiology and Immunology, College of Medicine, The University of Arizona, Tucson, AZ 85724, USAUS

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