Practice question

Domain architecture of kinesin-1 reveals clear division of labor essential for processive dimer motor function. N terminal globular motor domain about 340 amino acids contains P loop ATPase site switch I II microtubule binding interface and neck linker for mechanochemistry converting ATP hydrolysis to mechanical step. Immediately C terminal lies neck coiled coil ensuring dimerization of motor domains upon folding critical for hand over hand coordination followed by elongated stalk extending about 50 nm formed by interrupted coiled coil heptad repeats left handed supercoils stabilizing heavy chain dimer through hydrophobic packing of a and d positions leucine zipper like. Disruption of stalk by mutation prevents dimer formation and abolishes processivity yielding monomeric non processive motor. Central hinge regions provide flexibility for autoinhibited folding where C terminal tail interacts with motor domains to block ATPase until cargo binding unfolds. C terminal globular tail binds kinesin light chains via heptad interactions adapting to diverse vesicles mitochondria mRNA. Thus stalk responsible for dimerization via coiled coil interaction not ATP hydrolysis.