Final answer:
The key group of proteins that regulate the actin cytoskeleton is the Rho protein family.
Step-by-step explanation:
The key group of proteins that regulate the actin cytoskeleton is the Rho protein family. These proteins play a crucial role in controlling actin dynamics and cytoskeletal rearrangements. They are involved in various cellular processes such as cell migration, cell shape changes, and cytokinesis.