Practice question

Cytoplasmic dynein 1 is sole minus end directed microtubule motor powering retrograde intracellular transport complementary to kinesin superfamily anterograde transport systems establishing bidirectional highways. Structural features include two identical 530 kDa heavy chains dimerized at tail each with six concatenated AAA ATPase domains forming asymmetric ring linker that swings across ring coiled coil stalk ending in microtubule binding domain MTBD and cargo binding tail associated with intermediate light intermediate and light chains LC8 Tctex. Motor moves toward microtubule minus ends anchored near nucleus centrosome stepping 8 to 32 nm due to variable power stroke size and flexible stalk allowing large steps under load. Functions include transport of endosomes lysosomes autophagosomes mRNA nuclei centrosome positioning Golgi clustering perinuclearly and retrograde axonal transport of neurotrophic growth factors and injury signals. It does not transport cargo toward plus ends that is kinesin role; does not directly stabilize or crosslink microtubules independent of transport though cortical anchoring contributes to pulling forces on spindle. Its minus direction ensures inward delivery and centralization.