Figure 1. A schematic drawing illustrating the functional domains of a 90 kDa isoform of palladin polypeptide. In the testis, the predominant form of palladin detected by immunoblotting is the 90 kDa isoform, which is composed of a protein-rich region (PR region) for protein-protein interactions near its N terminus, and three IgC2 domains close to its C terminus for binding to F-actin to confer its F-actin cross-linking and F-actin bundling activity.