Fig. 1. Multiple palladin isoforms are transcribed from one gene. (A) Schematic representation of the gene structure of palladin. The murine palladin gene comprises at least 24 exons over 390 kb on chromosome 8 (Palld; cytoband B3.1). Transcripts are initiated from one of three nested promoters, which are indicated with arrowheads. (B) Schematic representation of the largest palladin isoform (200 kDa), which is transcribed from the most 5' promoter. The two proline-rich regions have been designated PR1 and PR2. (C) Schematic representation of mRNA splicing patterns for observed isoforms. Translation initiation and termination sites have been aligned with the above peptide sequence for the 200 kDa isoform. (D) Schematic representation of palladin isoforms. The 200 kDa, 140 kDa and 90 kDa isoforms are the primary products of the palladin gene and have been detected by immunoblotting. They share binding sequences for ezrin, -actinin, Ena/VASP family members and profilin. The 140 kDa and 200 kDa isoforms also encode two additional FPPPP motifs predicted to interact with Ena/VASP family members. Two other murine isoforms, designated N-terminus and C-terminus, have been reported at the cDNA level. Expression of the N-terminus isoform has not yet been directly confirmed.