Redβ177 annealase structure reveals details of oligomerization and λ Red-mediated homologous DNA recombination

Authors

Timothy P. Newing, University of Wollongong
Jodi L. Brewster, University of Wollongong
Lucy J. Fitschen, University of Wollongong
James C. Bouwer, University of Wollongong
Nikolas P. Johnston, University of Wollongong
Haibo Yu, University of Wollongong
Gökhan Tolun, University of Wollongong

Publication Name

Nature communications

Abstract

The Redβ protein of the bacteriophage λ red recombination system is a model annealase which catalyzes single-strand annealing homologous DNA recombination. Here we present the structure of a helical oligomeric annealing intermediate of Redβ, consisting of N-terminal residues 1-177 bound to two complementary 27mer oligonucleotides, determined via cryogenic electron microscopy (cryo-EM) to a final resolution of 3.3 Å. The structure reveals a continuous binding groove which positions and stabilizes complementary DNA strands in a planar orientation to facilitate base pairing via a network of hydrogen bonding. Definition of the inter-subunit interface provides a structural basis for the propensity of Redβ to oligomerize into functionally significant long helical filaments, a trait shared by most annealases. Our cryo-EM structure and molecular dynamics simulations suggest that residues 133-138 form a flexible loop which modulates access to the binding groove. More than half a century after its discovery, this combination of structural and computational observations has allowed us to propose molecular mechanisms for the actions of the model annealase Redβ, a defining member of the Redβ/RecT protein family.

Open Access Status

This publication may be available as open access

Volume

13

Issue

1

First Page

5649