Final answer:
Plakoglobin is not a component of focal adhesions; it is involved in cell-cell junctions, unlike integrin, talin, α-actinin, and vinculin, which are all part of focal adhesion complexes.
Step-by-step explanation:
The component that is not part of focal adhesions is plakoglobin. Focal adhesions are complex structures that provide anchorage for cells to their substrate via integrins, and they play a crucial role in signal transduction. Other components of focal adhesions include integrin, talin, α-actinin, and vinculin. These components are involved in the mechanical linkage and signaling mechanisms that are essential for a variety of cellular processes. Plakoglobin, on the other hand, is associated with cell-cell junctions such as adherens junctions and is not typically a component of focal adhesions. Instead, it is involved in linking cadherins to the intermediate filaments within the cytoplasm.