Protein, flagellin
Bacterial flagella are chemically composed of pure protein (a type of polymer), and the polymer is known as flagellin.
Bacterial flagella are whip-like appendages that extends from the cell body of certain bacteria. Bacteria mainly use the flagella for movement and it can also be used as a sensory organelle. Flagella have different structure, protein component and mechanism of propulsion. The bacterial flagella are helical shaped, thick hollow tubes that are chemically composed of the protein flagellin.