Figure 5.

Schematic modelling of the activation of kinesin-1 by the R₂KR₃ of RANBP2; R₂KR₃ is depicted as a cargo of KIF5B. Cargoless kinesin-1 is in a compact conformation with the tail folded over the motor domain causing the inhibition of the ATPase activity. At low concentrations, R₂KR₃ binds to one of the two bipartite binding sites in kinesin-1 and partly reverts the inhibition by the tails over its motor domain, generating an idle kinesin-1 with low ATPase activity (1). At high concentration of R₂KR₃ (2), the bipartite sites on both chains become occupied (3). This leads to an extended (relaxed) kinesin-1 by tight conformational coupling and boosting of the motor activity of kinesin-1 in the presence of microtubules (3). KIF5, kinesin superfamily protein 5; RANBP2, RAN-binding protein 2; R₂KR₃, RBD2–KBD–RBD3.