Flagellar radial spokes contribute to the regulation of dynein arm activity and thus the pattern of flagellar bending. They consist of a thin stalk, which is attached to the a subfiber of the outer doublet microtubule, and a bulbous head, which is attached to the stalk and appears to interact with the projections from the central pair of microtubules. Radial spoke. Asymmetrically dimethylated at Arg-191 and Arg-366 during flagellum resorption. Probably methylated by PRMT1. Belongs to the aldo/keto reductase family.