Fig. 6.

IRE RNA-binding activity in yeast extracts. RNA-binding activity was determined by gel-shift assay. (A) IRE RNA-binding activity was determined in yeast extracts as follows: lane 1, nontransformed; lane 2, WT IRP; lane 3, S711A; lane 4, S711D; lane 5, S711E; and lane 6, S711T. 1 nM RNA was used. (B) RNA-binding activity for transformants expressing WT or the S711 mutants of IRP1 plus nontransformed cells (n = 3 independent colonies). The spontaneous (gray bars) or 2% 2-mercaptoethanol-induced total (black bars) IRE RNA-binding activity was determined. (C) An RNA saturation analysis for extracts containing WT, S711D, or S711E IRP1.