Premium
Nucleoprotein architecture and ColE1 dimer resolution: a hypothesis
Author(s) -
Hodgman T. C.,
Griffiths H.,
Summers D. K.
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00948.x
Subject(s) - cole1 , biology , random hexamer , recombinase , nucleoprotein , repressor lexa , dna supercoil , dna , recombination , base pair , repressor , genetics , computational biology , plasmid , dna replication , microbiology and biotechnology , gene , transcription factor
Dimers of plasmid ColE1 are converted to monomers by site‐specific recombination, a process that requires 240 bp of DNA ( cer ) and four host‐encoded proteins (XerC, XerD, ArgR and PepA). Here, we propose structures for nucleoprotein complexes involved in cer –Xer recombination based upon existing knowledge of the structures of component proteins and computational analyses of protein structure and DNA curvature. We propose that, in the nucleoprotein complex at a single cer site, a PepA hexamer acts as an adaptor, connecting the heterodimeric recombinase (XerCD) to an ArgR hexamer. This provides a protein core around which the cer site wraps, its exact path being defined by strong sequence‐specific interactions with ArgR and XerCD, weak interactions with PepA and sequence‐dependent flexibility of cer . The initial association of single‐site complexes (pairing) is proposed to occur via an ArgR–PepA interaction. Pairing between sites in a plasmid dimer is stabilized by DNA supercoiling and is followed by a structural isomerization to form a recombination‐proficient synaptic complex. We propose that paired structures formed between sites in trans are too short‐lived to permit synaptic complex formation. There is thus an energetic barrier to inappropriate recombination reactions. Our proposals are consistent with a wide range of experimental observations.