Structure of phage λ Redβ177 annealase shows how it anneals DNA strands during single-strand annealing homologous DNA recombination (original) (raw)

The bacteriophage λ red recombination system catalyzes the single-strand annealing homologous DNA recombination reaction, in which Redβ annealase protein plays a critical role. Using cryogenic electron microscopy, we were able to determine a structure of a C-terminally truncated Redβ with the residues 1-177 bound to two complementary 27mer oligonucleotides forming an annealing intermediate, to a final resolution of 3.3 Å. This structure validates and rationalizes decades of experimental observations on the biochemistry of Redβ. Definition of the interaction surfaces between subunits explains not only the DNA binding properties of Redβ, but also its propensity to oligomerize into long helical filaments, which are also formed by almost all annealases and are known to be functionally important. In addition, this annealing intermediate structure provides a detailed picture of the hydrogen bonding network that positions the DNA strands in a planar orientation to facilitate base pairing. ...

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