DNA Polymerase C of the Thermophilic Bacterium Thermus aquaticus: Classification and Phylogenetic Analysis of the Family C DNA Polymerases |
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Authors: | Yi-Ping Huang Junetsu Ito |
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Institution: | (1) Department of Microbiology and Immunology, College of Medicine, The University of Arizona, Tucson, AZ 85724, USA, US |
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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.
Received: 7 October 1998 / Accepted: 12 January 1999 |
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Keywords: | : Family C DNA polymerases — Thermus aquaticus— Phylogeny — Classification of the family C DNA polymerases |
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