Targeting Allostery in the Dynein Motor Domain with Small Molecule Inhibitors
Cytoplasmic dyneins are AAA (ATPase associated with diverse cellular activities) motor proteins responsible for microtubule minus-end-directed intracellular transport. Dyneins unusually large size, four distinct nucleotide-binding sites, and the existence of closely-related isoforms with different functions, pose challenges for the design of potent and selective chemical inhibitors. Here we use structural approaches to develop a model for the inhibition of a well-characterized S. cerevisiae dynein construct by pyrazolo-pyrimidinone-based compounds. These data, along with single molecule experiments and mutagenesis studies, indicate that the compounds likely inhibit dynein by engaging the regulatory ATPase sites in the AAA3 and AAA4 domains, and not by interacting with dyneins main catalytic site in the AAA1 domain. A double Walker B mutant in AAA3 and AAA4 is an inactive enzyme, suggesting that inhibiting these regulatory sites can have a similar effect to inhibiting AAA1. Our findings reveal how chemical inhibitors can be designed to disrupt allosteric communication across dyneins AAA domains.