Kinesins

Kinesins are a family of microtubule-based motor proteins that convert ATP hydrolysis into mechanical work to move along microtubules. Most kinesins are plus-end–directed, transporting vesicles, organelles, and protein complexes toward the growing ends of microtubules, while a minority move toward the minus end.

Structurally, kinesins are typically dimers with two catalytic motor domains at the N-terminus, a coiled-coil stalk, and a tail that binds cargo via adaptor proteins. The conventional kinesin-1 (KIF5 family) moves by a hand-over-hand mechanism, taking 8-nanometer steps along a microtubule, powered by cycles of ATP binding, hydrolysis, and product release. The neck linker region directs force and stepping direction.

Diversity: many kinesins have specialized roles. KIF3 and KIF5 family members support anterograde transport in neurons; kinesin-2 motors participate in intraflagellar transport; kinesin-5 (Eg5/KIF11) motors power spindle bipolarity in mitosis; kinesin-14 family members are minus-end directed and contribute to spindle organization. Some kinesins act as microtubule depolymerases (kinesin-13).

Regulation and interaction: motor activity is regulated by autoinhibition, cargo binding, phosphorylation, and adaptor complexes that relieve inhibition and target kinesins to specific cargo.

Clinical and evolutionary context: defects in kinesin function are linked to neurodegenerative diseases and ciliopathies; kinesins are targets for anti-mitotic cancer therapies. The kinesin superfamily is diverse and conserved across eukaryotes, reflecting broad roles in intracellular transport and cell division.