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.
CD44 has been identified as a membrane-binding partner for ezrin/radixin/moesin (ERM) proteins, plasma membrane/actin filament cross-linkers. ERM proteins, however, are not necessarily colocalized with CD44 in tissues, but with CD43 and ICAM-2 in some types of cells. We found that glutathione-S-transferase fusion proteins with the cytoplasmic domain of CD43 and ICAM-2, as well as CD44, bound to moesin in vitro. The regions responsible for the in vitro binding of CD43 and CD44 to moesin were narrowed down to their juxta-membrane 20-30-amino acid sequences in the cytoplasmic domain. These sequences and the cytoplasmic domain of ICAM-2 (28 amino acids) were all characterized by the positively charged amino acid clusters. When E-cadherin chimeric molecules bearing these positively charged amino acid clusters of CD44, CD43, or ICAM-2 were expressed in mouse L fibroblasts, they were co-concentrated with ERM proteins at microvilli, whereas those lacking these clusters were diffusely distributed on the cell surface. The specific binding of ERM proteins to the juxta-membrane positively charged amino acid clusters of CD44, CD43, and ICAM-2 was confirmed by immunoprecipitation and site-directed mutagenesis. From these findings, we conclude that ERM proteins bind to integral membrane proteins bearing a positively charged amino acid cluster in their juxta-membrane cytoplasmic domain.
Pubmed ID: 9472040 RIS Download
Amino Acid Sequence | Amino Acids | Animals | Antigens, CD | Antigens, CD43 | Antigens, CD44 | Binding Sites | Blood Proteins | Cadherins | Cell Adhesion Molecules | Cells, Cultured | Cytoplasm | Cytoskeletal Proteins | Glutathione Transferase | L Cells (Cell Line) | Membrane Proteins | Mice | Microfilament Proteins | Microvilli | Molecular Sequence Data | Phosphoproteins | Precipitin Tests | Protein Binding | Protein Structure, Tertiary | Proteins | Recombinant Fusion Proteins | Sequence Homology, Amino Acid | Sialoglycoproteins | Transfection