Jergic, SlobodanOzawa, KiyoshiWilliams, NealSu, Xun-ChengScott, DanielHamdan, SamirCrowther, JeffreyDixon, NicholasOtting, Gottfried2009-06-262010-12-202009-06-262010-12-20Nucleic Acids Research 35.9 (2007): 2813-28240305-10481362-4962http://hdl.handle.net/10440/551http://digitalcollections.anu.edu.au/handle/10440/551The τ subunit of Escherichia coli DNA polymerase III holoenzyme interacts with the α subunit through its C-terminal Domain V,τC16. We show that the extreme C-terminal region of τC16 constitutes the site of interaction with α. The τC16 domain, but not a derivative of it with a C-terminal deletion of seven residues (τC16∆7), forms an isolable complex with α. Surface plasmon resonance measurements were used to determine the dissociation constant (KD) of the α–τC16 complex to be ~260 pM. Competition with immobilized τC16 by τC16 derivatives for binding to α gave values of KD of 7 µM for the α–τC16∆7 complex. Low-level expression of the genes encoding τC16 and τC16∆7, but not τC16∆11 is lethal to E. coli. Suppression of this lethal phenotype enabled selection of mutations in the 3' end of the τC16 gene, that led to defects in α binding. The data suggest that the unstructured C-terminus of τ becomes folded into a helix–loop–helix in its complex with α. An N-terminally extended construct, τC24, was found to bind DNA in a salt-sensitive manner while no binding was observed for τC16, suggesting that the processivity switch of the replisome functionally involves Domain IV of τ.12 pages"This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited." - from articleKeywords: DNA; DNA directed DNA polymerase gamma; holoenzyme; replisome; 3' untranslated region; alpha chain; amino terminal sequence; article; bacterial genetics; binding site; carboxy terminal sequence; complex formation; controlled study; dissociation constant;2007-03-1310.1093/nar/gkm0792015-12-08