To test the specificity of RNA binding activity of the in
vitro-phosphorylated recombinant calreticulin, we used a
mutant 3' (+)-SL RNA as a competitor in a RNA gel-shift
assay. In the 3' SL (AU) mutant RNA, A-U base pairs were
substituted for G-C base pairs, thereby maintaining the predicted
SL structure. In a gel-shift assay, recombinant calreticulin
interacted with RV RNA (Fig. 4E, lane 2) and the
binding activity was competed by the unlabeled wild-type 3'
(+)-SL RNA (Fig. 4E, lane 3) but not by the mutant RNA