Elucidation of Short Linear Motif-Based Interactions of the FERM Domains of Ezrin, Radixin, Moesin, and Merlin

The ERM (ezrin, radixin,and moesin) family of proteins and therelated protein merlin participate in scaffolding and signaling eventsat the cell cortex. The proteins share an N-terminal FERM [band four-point-one(4.1) ERM] domain composed of three subdomains (F1, F2, and F3) withbinding sites for short linear peptide motifs. By screening the FERMdomains of the ERMs and merlin against a phage library that displayspeptides representing the intrinsically disordered regions of thehuman proteome, we identified a large number of novel ligands. Wedetermined the affinities for the ERM and merlin FERM domains interactingwith 18 peptides and validated interactions with full-length proteinsthrough pull-down experiments. The majority of the peptides containedan apparent Yx-[FILV] motif; others show alternative motifs. We defineddistinct binding sites for two types of similar but distinct bindingmotifs (YxV and FYDF) using a combination of Rosetta FlexPepDock computationalpeptide docking protocols and mutational analysis. We provide a detailedmolecular understanding of how the two types of peptides with distinctmotifs bind to different sites on the moesin FERM phosphotyrosinebinding-like subdomain and uncover interdependencies between the differenttypes of ligands. The study expands the motif-based interactomes ofthe ERMs and merlin and suggests that the FERM domain acts as a switchableinteraction hub.