Thermus thermophilis dnaX homolog encoding gamma- and tau-like proteins of the chromosomal replicase

J Biol Chem. 1997 Oct 24;272(43):27131-9. doi: 10.1074/jbc.272.43.27131.


This report identifies the dnaX homolog from Thermus thermophilis. Replicases from bacteria to humans contain subunits that are homologous to one another. These homologs are subunits of a clamp loading apparatus that loads sliding clamps onto DNA, which in turn act as mobile tethers for the replication machinery. In Escherichia coli, two of these subunits (gamma and tau) are encoded by one gene (dnaX) in nearly equal amounts by way of an efficient translational frameshift. The gamma and tau subunits form the central touchpoint that holds together two DNA polymerases with one clamp loading apparatus to form the E. coli chromosomal replicase, DNA polymerase III holoenzyme. The E. coli holoenzyme is an efficient replication machine that simultaneously replicates both strands of duplex DNA. The T. thermophilis dnaX homolog also contains a frameshift signature and produces both tau- and gamma-like proteins. Recombinant T. thermophilis tau- and gamma-like proteins, expressed in E. coli, have an oligomeric state similar to that of their E. coli counterparts and display ATPase activity that is stimulated by DNA. These results imply that T. thermophilis utilizes a DNA polymerase III holoenzyme replication machinery similar to that of E. coli.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Amino Acid Sequence
  • Bacillus subtilis / enzymology
  • Bacteria / enzymology
  • Bacteria / genetics
  • Bacterial Proteins / biosynthesis*
  • Bacterial Proteins / chemistry
  • Base Sequence
  • Chromosomes, Bacterial / enzymology
  • Cloning, Molecular
  • Consensus Sequence
  • DNA Polymerase III / biosynthesis*
  • DNA Polymerase III / chemistry
  • DNA-Directed DNA Polymerase / biosynthesis*
  • DNA-Directed DNA Polymerase / chemistry
  • Escherichia coli / enzymology
  • Frameshifting, Ribosomal
  • Humans
  • Macromolecular Substances
  • Molecular Sequence Data
  • Nucleic Acid Conformation
  • RNA, Bacterial / chemistry
  • RNA, Bacterial / metabolism
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Ribosomes / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Thermus thermophilus / enzymology*
  • Thermus thermophilus / genetics*


  • Bacterial Proteins
  • DnaX protein, Bacteria
  • Macromolecular Substances
  • RNA, Bacterial
  • Recombinant Proteins
  • DNA replicase
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase
  • Adenosine Triphosphatases