MUTATIONAL ANALYSIS OF THE VACCINIA VIRUS E3 PROTEIN DEFINES AMINO-ACID-RESIDUES INVOLVED IN E3 BINDING TO DOUBLE-STRANDED-RNA

Alanine-substitution mutations were targeted to 14 amino acid residues within the double-stranded (ds) RNA binding motif (dsRBM) of the vacc inia virus E3 protein. Substitutions at six positions-Glu-124, Phe-135 , Phe-148, Lys-167, Arg-168, and Lys-171-caused significant reductions in dsRNA binding. These six residues are conserved in the two dsRBMs for which structural information is available (Escherichia coli RNase III and Drosophila melanogaster staufen) and in many other members of the dsRBM protein family. Residues we show to be important for dsRNA b inding by vaccinia virus E3 map to the same face of the dsRBM structur e and are thus likely to compose part of the RNA binding site.