Practice question

Long distance intracellular transport along microtubules employs directional motors whose motor domains read polarity via asymmetric binding and neck linker orientation. Majority of kinesin superfamily members possess N terminal motor domains that exhibit plus end directed motility via neck linker docking mechanism: ATP binding induces neck linker zippering toward plus end swinging trailing head forward 8 nm. Kinesin-1 KIF5B exemplifies conventional plus motor ferrying mitochondria synaptic vesicle precursors lysosomes and mRNP anterogradely toward cell periphery or axon terminals at about 1 micron per second. Dynein is obligate minus end directed motor moving cargo toward centrosome and nucleus for degradation. Myosin II operates on actin filaments for contractility not microtubules. Kinesin-14 family such as NCD and HSET moves minus end due to C terminal motor domain inverted orientation. Hence kinesin-1 epitomizes plus end cargo transport underlying polarized distribution peripheral positioning and axonal anterograde traffic essential for synaptic function and organelle inheritance during division.