title: DNA polymerase C of the thermophilic bacterium Thermus aquaticus: classification and phylogenetic analysis of the family C DNA polymerases.
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.
authors.affiliation: Department of Microbiology and Immunology, College of Medicine, The University of Arizona, Tucson, AZ 85724, USA.
authors.forename: Y P
authors.initials: YP
authors.lastname: Huang
authors.forename: J
authors.initials: J
authors.lastname: Ito
mesh_terms: D000595:Amino Acid Sequence; D001105:Archaea / Q000201:enzymology; D019843:Archaeal Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D019914:Taq Polymerase / Q000235:genetics; D013824:Thermus / Q000201:enzymology* / Q000235:genetics
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; C040220:DNA polymerase C; D009713:Nucleotidyltransferases; D019914:Taq Polymerase