What happens to dynein when ATP binds to its AAA1 domain?
Nucleotide dependent affinity switching allows dynein stepping without dragging cargo backward and enables high force production. In high affinity state stalk MTBD binds tightly to microtubule lattice resisting detachment under piconewton loads up to 7 pN corresponding to apo or ADP bound heavy chain state with stalk helices registry CC1 CC2 in specific alignment. When ATP enters AAA1 pocket AAA ring closure pulls AAA5 and buttress subdomains sliding stalk coiled coils by half heptad altering MTBD helices arrangement converting to low affinity conformation reducing binding energy about tenfold causing rapid detachment within milliseconds from track enabling motor to diffuse forward and execute priming stroke where linker bends away from ring. Hydrolysis restores high affinity allowing reattachment a few tubulin dimers toward minus end about 8 nm displacement. This detach mechanism parallels myosin where ATP binding also dissociates rigor actomyosin linkage though dynein uses AAA ring allostery rather than direct cleft opening of actin binding site. Without transient detachment upon ATP binding motor would remain locked unable to step processively essential for transport under load.
Ref: Imamula et al., Cell 2007 – Detachment upon ATP binding to AAA1 causes dynein release.