The ERM family consists of three closely-related proteins, ezrin, radixin and moesin [1,2]. Ezrin was first identified as a constituent of microvilli, radixin as a barbed, end-capping actin-modulating protein from isolated junctional fractions, and moesin as a heparin binding protein [4]. A tumour suppressor molecule responsible for neurofibromatosis type 2 (NF2) is highly similar to ERM proteins and has been designated merlin (moesin-ezrin-radixin-like protein) [3]. ERM molecules contain 3 domains, an N-terminal globular domain, an extended alpha-helical domain and a charged C-terminal domain (Pfam:PF00769) [2]. Ezrin, radixin and merlin also contain a polyproline linker region between the helical and C-terminal domains. The N-terminal domain is highly conserved and is also found in merlin, band 4.1 proteins and members of the band 4.1 superfamily, designated the FERM domain. ERM proteins crosslink actin filaments with plasma membranes. They co-localise with CD44 at actin filament plasma membrane interaction sites, associating with CD44 via their N-terminal domains and with actin filaments via their C-terminal domains [2]. This is the alpha-helical domain, which is involved in intramolecular masking of protein-protein interaction sites, regulating the activity of this proteins [5,6].

1: Ezrin/radixin/moesin (ERM) proteins bind to a positively charged amino acid cluster in the juxta-membrane cytoplasmic domain of CD44, CD43, and ICAM-2. Yonemura S, Hirao M, Doi Y, Takahashi N, Kondo T, Tsukita S; J Cell Biol 1998;140:885-895. PMID:9472040

2: ERM proteins: head-to-tail regulation of actin-plasma membrane interaction. Tsukita S, Yonemura S, Tsukita S; Trends Biochem Sci. 1997;22:53-58. PMID:9048483

3: Moesin-ezrin-radixin-like protein (merlin) mediates protein interacting with the carboxyl terminus-1 (PICT-1)-induced growth inhibition of glioblastoma cells in the nucleus. Chen H, Mei L, Zhou L, Zhang X, Guo C, Li J, Wang H, Zhu Y, Zheng Y, Huang L; Int J Biochem Cell Biol. 2011;43:545-555. PMID:21167305

4: X-linked primary immunodeficiency associated with hemizygous mutations in the moesin (MSN) gene. Lagresle-Peyrou C, Luce S, Ouchani F, Soheili TS, Sadek H, Chouteau M, Durand A, Pic I, Majewski J, Brouzes C, Lambert N, Bohineust A, Verhoeyen E, Cosset FL, Magerus-Chatinet A, Rieux-Laucat F, Gandemer V, Monnier D, Heijmans C, van Gijn M, Dalm VA, Mahlaoui N, Stephan JL, Picard C, Durandy A, Kracker S, Hivroz C, Jabado N, de Saint Basile G, Fischer A, Cavazzana M, Andre-Schmutz I; J Allergy Clin Immunol. 2016;138:1681-1689. PMID:27405666

5: Self-masking in an intact ERM-merlin protein: an active role for the central alpha-helical domain. Li Q, Nance MR, Kulikauskas R, Nyberg K, Fehon R, Karplus PA, Bretscher A, Tesmer JJ; J Mol Biol. 2007;365:1446-1459. PMID:17134719

6: Structural characterization suggests models for monomeric and dimeric forms of full-length ezrin. Phang JM, Harrop SJ, Duff AP, Sokolova AV, Crossett B, Walsh JC, Beckham SA, Nguyen CD, Davies RB, Glockner C, Bromley EH, Wilk KE, Curmi PM; Biochem J. 2016;473:2763-2782. PMID:27364155