Kinesin motor domain, BimC/Eg5 spindle pole proteins
Kinesin motor domain, BimC/Eg5 spindle pole proteins, participate in spindle assembly and chromosome segregation during cell division. This catalytic (head) domain has ATPase activity and belongs to the larger group of P-loop NTPases. Kinesins are microtubule-dependent molecular motors that play important roles in intracellular transport and in cell division. In most kinesins, the motor domain is found at the N-terminus (N-type), N-type kinesins are (+) end-directed motors, i.e. they transport cargo towards the (+) end of the microtubule. Kinesin motor domains hydrolyze ATP at a rate of about 80 per second, and move along the microtubule at a speed of about 6400 Angstroms per second. To achieve that, kinesin head groups work in pairs. Upon replacing ADP with ATP, a kinesin motor domain increases its affinity for microtubule binding and locks in place. Also, the neck linker binds to the motor domain, which repositions the other head domain through the coiled-coil domain close to a second tubulin dimer, about 80 Angstroms along the microtubule. Meanwhile, ATP hydrolysis takes place, and when the second head domain binds to the microtubule, the first domain again replaces ADP with ATP, triggering a conformational change that pulls the first domain forward.
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