Localization of CFTR-binding site on the rod 2 segment, IgFLNa15–24. A, GST immunoblot (IB) of CFTR1–25 peptide pulldowns from purified GST-tagged FLNa repeats. B, His-16–24 and deletion mutant (Δ17,19,21,23 deletion of IgFLNa17, 19, 21, and 23) were pulled down with increasing amounts of the wild-type (WT) or S13F mutant CFTR1–25 peptide. Bound protein was detected by immunoblotting using anti-His mAb conjugated with peroxidase.