| Autor: |
Pritchard, Arthur E., Dallmann, H. Garry, Glover, Bradley P., McHenry, Charles S. |
| Předmět: |
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| Zdroj: |
EMBO Journal; 12/1/2000, Vol. 19 Issue 23, p6536-6545, 10p |
| Abstrakt: |
We have constructed a plasmid-borne artificial operon that expresses the six subunits of the DnaX complex of Escherichia coli DNA polymerase III holoenzyme: τ, γ, δ, δ′, χ and ψ. Induction of this operon followed by assembly in vivo produced two τγ mixed DnaX complexes with stoichiometries of τlγ2δδ′χψ and τ2γ1δδ′χψ rather than the expected γ2τ2δδ′χψ. We observed the same heterogeneity when τγ mixed DnaX complexes were reconstituted in vitro. Re-examination of homomeric DnaX τ and γ complexes assembled either in vitro or in vivo also revealed a stoichiometry of DnaX3δδ′χψ. 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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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