Abstract
We propose a dynamic mechanism for the processive motility of dynein on microtubules (MTs). The force generated for the motion of dynein is purely mechanical in origin. When a dynein monomer binds to a MT, the AAA ring of dynein might fit into one of the trenches on the outer surface of the MT, with the linker domain leaning on the ratchet-shaped protofilament. At room temperature, the dynein molecule exhibits random thermal motion on the outer surface of the MT. The collision between the asymmetric ratchet teeth and the linker exerts a reactive impulsive force on the dynein molecule. The probability of producing an impulse with a longitudinal component pointing to either end of the MT depends on the instantaneous motion of dynein, the shape of the linker, and the mass distribution of the dynein with/without a load. In the dynamic mechanism, dynein monomers can move independently and processively toward either end of the MT. Many observations of the motility of dynein can be reproduced in a simulation system.
Highlights
Cytoplasmic dyneins are dimeric molecular motors that transport various intramolecular cargoes toward the minus end of microtubules (MTs) [1]-[7]
When the MT-binding domain (MTBD) of the dynein monomer binds to the MT, the AAA ring of dynein might fit into one of the trenches, with the linker domain leaning on the ratchet-shaped protofilament
The main purpose of this part of experiments is to demonstrate the effects of symmetry by the shift of center of mass (CM), the simulation MTBD is disconnected so that CM of the symmetric simulation dynein is on the vertical axis
Summary
Cytoplasmic dyneins are dimeric molecular motors that transport various intramolecular cargoes toward the minus end of microtubules (MTs) [1]-[7]. Dynein can slide two MTs across each other by the separate binding of monomers to two MTs [17] These observations suggest that the monomers can move independently on MTs. Recent studies have demonstrated that the individual rat brain cytoplasmic dynein dimer does not move processively on MTs, but moves processively on MTs after forming a complex with dynactin and a cargo adapter [18]-[20]. Because complex formation at the distal, flexible tail domain rarely affects the internal conformational changes, the motility of dynein may not be related to the internal conformation changes, at least for rat cytoplasmic dynein.
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