FIG. 6.

EMSA of wild-type and mutant PRE fragment III binding to GST-PTB. (A) ³²P-labeled wild-type fragment III, mutant 33, or mutant 34 was incubated with the indicated amount of GST-PTB and then electrophoresed on a native polyacrylamide gel. Mutants 33 and 34 contain clustered point mutations in sites 1 and 2, respectively (Fig. 4). (B) ³²P-labeled wild-type fragment III or mutant 39 was incubated with the indicated amount of GST-PTB and then electrophoresed on a native polyacrylamide gel. Mutant 39 contains clustered point mutations between sites 1 and 2 (Fig. 4).