A new 82-kD barbed end-capping protein (radixin) localized in the cell-to-cell adherens junction: purification and characterization.
An 82-kD protein has been purified from the undercoat of the adherens junction isolated from the rat liver. The purification scheme includes low salt extraction followed by DEAE-cellulose ion exchange, DNase I-actin affinity, and carboxyl methyl-cellulose ion exchange chromatographies. The purified 82-kD protein was essentially free of contaminants as judged by SDS-PAGE combined with silver staining. The substoichiometric 82-kD protein largely inhibited the actin filament assembly; when the molar ratio of the 82-kD protein to G-actin was 1:1,000, the viscosity was reduced to 28% of the control value. Direct electron microscopic studies revealed that the 82-kD protein selectively inhibited monomer addition at the barbed ends of actin filaments. By use of the antibody raised against the 82-kD protein, this protein was shown by immunofluorescence microscopy to be localized at the cell-to-cell adherens junction in various types of cells. In contrast, the 82-kD protein was not concentrated at the cell-to-substrate adherens junctions (focal contacts). These findings have led us to conclude that the 82-kD protein is a barbed end-capping protein which is associated with the undercoat of the cell-to-cell adherens junction. Hence, we have tentatively designated the 82-kD protein as radixin (from the Latin word radix meaning root).
Tsukita
S
S
Department of Ultrastructural Research, Tokyo Metropolitan Institute of Medical Science, Japan.
Hieda
Y
Y
Tsukita
S
S
D000177:Acrosome / Q000648:ultrastructure; D008841:Actin Cytoskeleton / Q000648:ultrastructure*; D000199:Actins / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002846:Chromatography, Affinity; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000648:ultrastructure*; D051180:Desmoplakins; D005455:Fluorescent Antibody Technique; D007365:Intercellular Junctions / Q000648:ultrastructure*; D008099:Liver / Q000032:analysis / Q000648:ultrastructure; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000302:isolation & purification* / Q000378:metabolism; D008970:Molecular Weight; D009124:Muscle Proteins / Q000378:metabolism; D051381:Rats; D016596:Vinculin; D014783:Viscosity
D000199:Actins; D003598:Cytoskeletal Proteins; D051180:Desmoplakins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D016596:Vinculin