A novel assembly mechanism for the DNA polymerase III holoenzyme DnaX complex: association of deltadelta' with DnaX(4) forms DnaX(3)deltadelta'. Journal Article uri icon



  • We have constructed a plasmid-borne artificial operon that expresses the six subunits of the DnaX complex of Escherichia coli DNA polymerase III holoenzyme: tau, gamma, delta, delta', chi and psi. Induction of this operon followed by assembly in vivo produced two taugamma mixed DnaX complexes with stoichiometries of tau(1)gamma(2)deltadelta'chipsi and tau(2)gamma(1)deltadelta'chipsi rather than the expected gamma(2)tau(2)deltadelta'chipsi. We observed the same heterogeneity when taugamma mixed DnaX complexes were reconstituted in vitro. Re-examination of homomeric DnaX tau and gamma complexes assembled either in vitro or in vivo also revealed a stoichiometry of DnaX(3)deltadelta'chipsi. Equilibrium sedimentation analysis showed that free DnaX is a tetramer in equilibrium with a free monomer. An assembly mechanism, in which the association of heterologous subunits with a homomeric complex alters the stoichiometry of the homomeric assembly, is without precedent. The significance of our findings to the architecture of the holoenzyme and the clamp-assembly apparatus of all other organisms is discussed.

publication date

  • December 1, 2000

has subject area

has restriction

  • green

Date in CU Experts

  • October 1, 2013 12:09 PM

Full Author List

  • Pritchard AE; Dallmann HG; Glover BP; McHenry CS

author count

  • 4

Other Profiles

International Standard Serial Number (ISSN)

  • 0261-4189

Additional Document Info

start page

  • 6536

end page

  • 6545


  • 19


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