title: The hyperthermophilic bacterium Thermotoga maritima has two different classes of family C DNA polymerases: evolutionary implications.
abstract: Bacterial DNA polymerase III (family C DNA polymerase), the principal chromosomal replicative enzyme, is known to occur in at least three distinct forms which have provisionally been classified as class I ( Escherichia coli DNA pol C-type), class II ( Bacillus subtilis DNA pol C-type) and class III (cyanobacteria DNA pol C-type). We have identified two family C DNA polymerase sequences in the hyperthermophilic bacterium Thermotoga maritima. One DNA polymerase consisting of 842 amino acid residues and having a molecular weight of 97 213 belongs to class I. The other one, consisting of 1367 amino acid residues and having a molecular weight of 155 361, is a member of class II. Comparative sequence analyses suggest that the class II DNA polymerase is the principal DNA replicative enzyme of the microbe and that the class I DNA polymerase may be functionally inactive. A phylogenetic analysis using the class II enzyme indicates that T.maritima is closely related to the low G+C Gram-positive bacteria, in particular to Clostridium acetobutylicum, and mycoplasmas. These results are in conflict with 16S rRNA-based phylogenies, which placed T.maritima as one of the deepest branches of the bacterial tree.
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; D001426:Bacterial Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics*; D003062:Codon / Q000737:chemistry; D004258:DNA Polymerase III / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000737:chemistry* / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020124:Thermotoga maritima / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D003062:Codon; C040220:DNA polymerase C; C074904:DNA polymerase III, alpha subunit; D009713:Nucleotidyltransferases; D004258:DNA Polymerase III