Sequence and domain structure of talin

TALIN is a high-molecular-weight cytoskeletal protein concentrated at regions of cell-substratum contact¹ and, in lymphocytes, at cell-cell contacts^2,3. Integrin receptors are involved in the attachment of adherent cells to extracellular matrices^4,5 and of lymphocytes to other cells⁶. In these situations, talin codistributes with concentrations of integrins in the cell surface membrane^3,7-9. Furthermore, in vitro binding studies suggest that integrins bind to talin, although with low affinity¹⁰. Talin also binds with high affinity to vinculin¹¹, another cytoskeletal protein concentrated at points of cell adhesion¹². Finally, talin is a substrate for the Ca²⁺-activated protease, calpain II^13,14, which is also concentrated at points of cell-substratum contact¹⁴. To learn more about the structure of talin and its involvement in transmembrane connections between extracellular adhesions and the cytoskeleton, we have cloned and sequenced murine talin. We describe a model for the structure of talin based on this sequence and other data. Homologies between talin and other proteins define a novel family of submembranous cytoskeleton-associated proteins all apparently involved in connections to the plasma membrane.