Radial spoke

The radial spoke is a multi-unit protein structure found in the axonemes of eukaryotic cilia and flagella.

[1] Although experiments have determined the importance of the radial spoke in the proper function of these organelles, its structure and mode of action remain poorly understood.

Radial spokes are T-shaped structures present inside the axoneme.

Each spoke consists of a "head" and a "stalk," while each of these sub-structures is itself made up of many protein subunits.

For example, mutant organisms lacking properly functioning radial spokes have flagella and cilia that are immotile.