Fig. 3. The 3' zipcode binds a subset of the 5'-zipcode-binding proteins isolated from rat brain protein extracts. (A) Coomassie-blue-stained SDS/polyacrylamide gel showing rat brain proteins that bound to magnetic particles bearing immobilized ß-actin mRNA 5' zipcode (5'ZIP) or the 3' zipcode (3'ZIP). The bands identified by Edman sequencing are marked on the right. In this experiment, as in others we have performed, the level of hnRNP L was higher than in the experiment shown in Fig. 1. The positions of standard proteins are shown on the left, with molecular masses in kDa. (B) Western blotting of proteins from pull-down experiments performed with immobilized A2RE11, 5'ZIP and 3'ZIP showed that hnRNP A2 does not bind the 5' zipcode or 3' zipcode. The blot was developed with hnRNP A2 antibody as the primary antibody. Protein bands were detected with an alkaline-phosphatase-conjugated secondary antibody.