Fig. 1. Biochemical characterization of Staufen dsRBD3 interaction with RNA stem–loops. North-western blots showing (A) binding of wild-type dsRBD3 to RNA stem–loops and (B) alanine-scanning mutagenesis of dsRBD3. The top panel shows the positions of the amino acids that were substituted, with a diagram of the secondary structure of the domain underneath. The numbering refers to the general dsRBD alignment scheme; Pro1 corresponds to Pro579 in Drosophila Staufen. Green residues correspond to mutated amino acids required for the correct folding of the domain, while red residues are surface exposed. A black arrow indicates no RNA binding; grey arrow, reduced binding; no arrow indicates that the mutation had no effect. The lower panel shows a representative blot of the alanine substitution mutants probed with double-stranded VA1 RNA. The same amount of protein was present in each lane (data not shown).