Which of the following statements about dynein heavy chains is TRUE?
Dynein heavy chains define motor identity through massive size and AAA ATPase ring arrangement unique among cytoskeletal motors distinguishable from kinesin and myosin smallest motors. Each 530 kDa heavy chain encodes six AAA plus repeats arranged in asymmetric ring with seventh pseudo AAA domain closing structure. AAA1 through AAA4 contain P loop Walker A motifs capable of nucleotide binding AAA1 major catalytic site hydrolyzing ATP for movement AAA2 through AAA4 bind ATP regulatory maintaining ring closure and coordinating allostery. AAA5 AAA6 structural no nucleotide hydrolysis. Linker arching over ring converts ring conformational wave to power stroke directed toward minus end. Unlike myosin containing actin binding cleft in motor domain dynein heavy chains possess separate stalk MTBD projecting from AAA4 no actin interaction ever. They do not polymerize into filaments but operate as obligate dimers via tail dimerization domain. Statements claiming actin binding or filament formation incorrect and inconsistent with biochemical assays. True distinguishing characteristic presence of ATPase domains within hexameric AAA ring converting ATP chemical energy to minus end movement and force generation for transport.
Ref: Roberts et al., Cell 2013 – Dynein heavy chain has ATPase domains within AAA+ ring true statement architecture.