Final answer:
The accessory protein that stabilizes intermediate filaments is plectin.
Step-by-step explanation:
Accessory proteins called plectin stabilize intermediate filaments. Intermediate filaments are a type of cytoskeletal filament made of keratin that provide structural support to cells and resist tension. Plectin plays a role in connecting intermediate filaments to other cellular structures, such as cell membranes and organelles, ensuring their stability.