title: RecOR complex including RecR N-N dimer and RecO monomer displays a high affinity for ssDNA.
abstract: RecR is an important recombination mediator protein in the RecFOR pathway. RecR together with RecO and RecF facilitates RecA nucleoprotein filament formation and homologous pairing. Structural and biochemical studies of Thermoanaerobacter tengcongensis RecR (TTERecR) and its series mutants revealed that TTERecR uses the N-N dimer as a basic functional unit to interact with TTERecO monomer. Two TTERecR N-N dimers form a ring-shaped tetramer via an interaction between their C-terminal regions. The tetramer is a result of crystallization only. Hydrophobic interactions between the entire helix-hairpin-helix domains within the N-terminal regions of two TTERecR monomers are necessary for formation of a RecR functional N-N dimer. The TTERecR N-N dimer conformation also affects formation of a hydrophobic patch, which creates a binding site for TTERecO in the TTERecR Toprim domain. In addition, we demonstrate that TTERecR does not bind single-stranded DNA (ssDNA) and binds double-stranded DNA very weakly, whereas TTERecOR complex can stably bind DNA, with a higher affinity for ssDNA than double-stranded DNA. Based on these results, we propose an interaction model for the RecOR:ssDNA complex.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Qun
authors.initials: Q
authors.lastname: Tang
authors.forename: Pu
authors.initials: P
authors.lastname: Gao
authors.forename: Yan-Ping
authors.initials: YP
authors.lastname: Liu
authors.forename: Ang
authors.initials: A
authors.lastname: Gao
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: An
authors.forename: Shun
authors.initials: S
authors.lastname: Liu
authors.forename: Xiao-Xue
authors.initials: XX
authors.lastname: Yan
authors.forename: Dong-Cai
authors.initials: DC
authors.lastname: Liang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D019281:Dimerization; D008239:Lysine / Q000737:chemistry; D008958:Models, Molecular; D011485:Protein Binding; D055503:Protein Multimerization; D046968:Thermoanaerobacter
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; C065831:RecR protein, Bacteria; D008239:Lysine