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 the
related protein merlin participate in scaffolding and signaling events
at 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) with
binding sites for short linear peptide motifs. By screening the FERM
domains of the ERMs and merlin against a phage library that displays
peptides representing the intrinsically disordered regions of the
human proteome, we identified a large number of novel ligands. We
determined the affinities for the ERM and merlin FERM domains interacting
with 18 peptides and validated interactions with full-length proteins
through pull-down experiments. The majority of the peptides contained
an apparent Yx[FILV] motif; others show alternative motifs. We defined
distinct binding sites for two types of similar but distinct binding
motifs (YxV and FYDF) using a combination of Rosetta FlexPepDock computational
peptide docking protocols and mutational analysis. We provide a detailed
molecular understanding of how the two types of peptides with distinct
motifs bind to different sites on the moesin FERM phosphotyrosine
binding-like subdomain and uncover interdependencies between the different
types of ligands. The study expands the motif-based interactomes of
the ERMs and merlin and suggests that the FERM domain acts as a switchable
interaction hub.