The recombination-associated protein RdgC adopts a novel toroidal architecture for DNA binding |
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Authors: | Ha Jun Yong Kim Hye Kyong Kim Do Jin Kim Kyoung Hoon Oh Sung Jin Lee Hyung Ho Yoon Hye Jin Song Hyun Kyu Suh Se Won |
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Institution: | Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-742, Korea. |
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Abstract: | RecA plays a central role in the nonmutagenic repair of stalled replication forks in bacteria. RdgC, a recombination-associated DNA-binding protein, is a potential negative regulator of RecA function. Here, we have determined the crystal structure of RdgC from Pseudomonas aeruginosa. The J-shaped monomer has a unique fold and can be divided into three structural domains: tip domain, center domain and base domain. Two such monomers dimerize to form a ring-shaped molecule of approximate 2-fold symmetry. Of the two inter-subunit interfaces within the dimer, one interface (‘interface A’) between tip/center domains is more nonpolar than the other (‘interface B’) between base domains. The structure allows us to propose that the RdgC dimer binds dsDNA through the central hole of ~30 Å diameter. The proposed model is supported by our DNA-binding assays coupled with mutagenesis, which indicate that the conserved positively charged residues on the protein surface around the central hole play important roles in DNA binding. The novel ring-shaped architecture of the RdgC dimer has significant implications for its role in homologous recombination. |
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