Dyneinarmen

Dyneinarmen refers to the dynein motor protein complexes that are associated with the axoneme of motile cilia and flagella. They play a central role in generating the bending motions of these organelles by converting chemical energy from ATP hydrolysis into mechanical work, producing sliding forces between adjacent microtubule doublets.

Structure and composition involve two main classes: outer dynein arms and inner dynein arms. Each arm is a multi-subunit complex, typically including heavy chains that provide force generation, along with intermediate and light chains that contribute to assembly, stability, and regulation. The arms are anchored to the A-tubule of one microtubule and project toward the neighboring B-tubule, enabling coordinated microtubule sliding along the length of the cilium or flagellum.

Mechanistically, dyneinarmen hydrolyze ATP to power conformational changes in the heavy chains, which produce a force that tug the microtubules past one another. The resulting sliding is converted into a rhythmic bend by the structural constraints of the axoneme, including linking proteins and the radial spoke–dynein regulatory complex network that coordinates activity across arms and doublets.

Regulation and coordination are essential for proper beat patterns. Nexin links and regulatory complexes modulate dynein activity to prevent uncoordinated sliding, producing the characteristic oscillatory motion necessary for propulsion or fluid movement.

Clinical relevance includes defects in dyneinarmen contributing to primary ciliary dyskinesia, a spectrum of disorders marked by impaired mucociliary clearance, chronic respiratory infections, and sometimes situs inversus due to disrupted left-right asymmetry during development.

See also: cilia, flagella, axoneme, dynein, primary ciliary dyskinesia.