Fig. 2.

The R domain is encoded by a lineage-specific expansion of exons 14 and 15 in CFTR relative to ABCC4. (A) Correspondence between CFTR and ABCC4 exons (based on the alignment shown in Supplementary Fig. 3). Corresponding exonic regions are placed in the same column, and exons (or exonic regions) that do not have corresponding sequences are marked with 0. Locations of CFTR domains are indicated above. (B) Visual scheme of BLAST results showing local sequence similarity between CFTR and ABCC subfamily members in exon 13 and the 5′ end of exon 14 along with the R domain insertion in CFTR exon 14. (C) Amino acid sequence alignment between CFTR and ABCC subfamily members corresponding to the protein region encoded by exon 13 and the 5′ end of exon 14. The location of the CFTR-specific R domain extension and its sequence are shown.