Flagellin
![Helicobacter pylori electron micrograph, showing multiple flagella on the cell surface](/Images/godic/202501/13/EMpylori0550.jpg")
Flagellin is a globular protein that arranges itself in a hollow cylinder to form the filament in a bacterial flagellum. It has a mass of about 30,000 to 60,000 daltons. Flagellin is the principal substituent of bacterial flagellum, and is present in large amounts on nearly all flagellated bacteria.