Ezrin has a COOH-terminal actin-binding site that is conserved in the ezrin protein family.
Ezrin, previously also known as cytovillin, p81, and 80K, is a cytoplasmic protein enriched in microvilli and other cell surface structures. Ezrin is postulated to have a membrane-cytoskeleton linker role. Recent findings have also revealed that the NH2-terminal domain of ezrin is associated with the plasma membrane and the COOH-terminal domain with the cytoskeleton (Algrain, M., O. Turunen, A. Vaheri, D. Louvard, and M. Arpin. 1993. J. Cell Biol. 120: 129-139). Using bacterially expressed fragments of ezrin we now demonstrate that ezrin has an actin-binding capability. We used glutathione-S-transferase fusion proteins of truncated ezrin in affinity chromatography to bind actin from the cell extract or purified rabbit muscle actin. We detected a binding site for filamentous actin that was localized to the COOH-terminal 34 amino acids of ezrin. No binding of monomeric actin was detected in the assay. The region corresponding to the COOH-terminal actin-binding site in ezrin is highly conserved in moesin, actin-capping protein radixin and EM10 protein of E. multilocularis, but not in merlin/schwannomin. Consequently, this site is a potential actin-binding site also in the other members of the protein family. Furthermore, the actin-binding site in ezrin shows sequence homology to the actin-binding site in the COOH terminus of the beta subunit of the actin-capping protein CapZ and one of the potential actin-binding sites in myosin heavy chain. The actin-binding capability of ezrin supports its proposed role as a membrane-cytoskeleton linker.
Turunen
O
O
Haartman Institute, Department of Virology, Helsinki University, Finland.
Wahlström
T
T
Vaheri
A
A
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002846:Chromatography, Affinity; D017124:Conserved Sequence; D003598:Cytoskeletal Proteins; D004926:Escherichia coli; D005982:Glutathione Transferase; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D014407:Tumor Cells, Cultured; D000099149:Ezrin
D000199:Actins; D003598:Cytoskeletal Proteins; D005982:Glutathione Transferase; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D000099149:Ezrin