The structure of the flock house virus B2 protein, a viral suppressor of RNA interference, shows a novel mode of double-stranded RNA recognition

We report the structure of the flock house virus B2 protein, a potent suppressor of RNA interference (RNAi) in animals and plants. The B2 protein is a homodimer in solution and contains three alpha-helices per monomer. Chemical shift perturbation shows that an antiparallel arrangement of helices (alpha 2/alpha 2') forms an elongated binding interface with double-stranded RNA (dsRNA). This implies a novel mode of dsRNA recognition and provides insights into the mechanism of RNAi suppression by B2.