PROSITE documentation PDOC00412
DNA polymerase family A signature


Replicative DNA polymerases (EC are the key enzymes catalyzing the accurate replication of DNA. They require either a small RNA molecule or a protein as a primer for the de novo synthesis of a DNA chain. On the basis of sequence similarities a number of DNA polymerases have been grouped together [1,2,3] under the designation of DNA polymerase family A. The polymerases that belong to this family are listed below.

  • Escherichia coli and various other bacterial polymerase I (gene polA).
  • Thermus aquaticus Taq polymerase.
  • Bacteriophage sp01 polymerase.
  • Bacteriophage sp02 polymerase.
  • Bacteriophage T5 polymerase.
  • Bacteriophage T7 polymerase.
  • Mycobacteriophage L5 polymerase.
  • Yeast mitochondrial polymerase γ (gene MIP1).

Five regions of similarity are found in all the above polymerases. One of these conserved regions, known as 'motif B' [1], is located in a domain which, in Escherichia coli polA, has been shown to bind deoxynucleotide triphosphate substrates; it contains a conserved tyrosine which has been shown, by photo-affinity labelling, to be in the active site; a conserved lysine, also part of this motif, can be chemically labelled, using pyridoxal phosphate. We use this conserved region as a signature for this family of DNA polymerases.

Last update:

November 1995 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

DNA_POLYMERASE_A, PS00447; DNA polymerase family A signature  (PATTERN)


1AuthorsDelarue M. Poch O. Tordo N. Moras D. Argos P.
TitleAn attempt to unify the structure of polymerases.
SourceProtein Eng. 3:461-467(1990).
PubMed ID2196557

2AuthorsIto J. Braithwaite D.K.
TitleCompilation and alignment of DNA polymerase sequences.
SourceNucleic Acids Res. 19:4045-4057(1991).
PubMed ID1870963

3AuthorsBraithwaite D.K. Ito J.
TitleCompilation, alignment, and phylogenetic relationships of DNA polymerases.
SourceNucleic Acids Res. 21:787-802(1993).
PubMed ID8451181

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