Practice question

Dynein heavy chain organization subdivided into distinct functional modules arranged linearly from N to C terminus: tail stem region for cargo adaptor binding and dimerization via intermediate chain interactions, motor ring core, and stalk linker elements bridging. Tail contains dimerization domain plus binding sites for light intermediate chains controlling cargo selectivity not microtubule binding. Central motor ring of six AAA domains AAA1 to AAA6 forming closed asymmetric ring plus protruding antiparallel coiled coil stalk emerging between AAA4 small and large subdomains after second coiled coil sequence. At tip of stalk small globular microtubule binding domain MTBD consisting of six helices H1 to H6 that directly contacts alpha beta tubulin at intradimer interface between protofilaments. Conformational changes in ring driven by AAA1 ATP hydrolysis cause sliding of coiled coil helices within stalk altering MTBD affinity registry from high to low switching. Linker domain connects tail to ring and bends during power stroke converting ring closure to directional movement. Cargo binding domain separate near N terminus distinct from stalk. Therefore domain containing microtubule binding region is stalk domain linking motor ring to track.