Kinesines

Kinesins are a large and evolutionarily conserved family of microtubule-based motor proteins that transport cargo within eukaryotic cells. They convert chemical energy from ATP hydrolysis into mechanical work, enabling movement along microtubules and the delivery of vesicles, organelles, protein complexes, and mRNA.

Most kinesins are dimeric, with two motor domains that bind microtubules and ATP. The motor domain is typically at the N-terminus, followed by a coiled-coil stalk that drives dimerization and a C-terminal tail that recognizes cargo via adaptor proteins. Through a chemomechanical cycle, ATP binding, hydrolysis, and product release drive conformational changes that cause one head to step forward in a hand-over-hand sequence, producing processive movement in 8-nm increments.

Directionality is mostly toward the microtubule plus end, enabling transport toward the cell periphery; however, some kinesins, such as kinesin-14, move toward the minus end and contribute to spindle organization and other tasks. Functional roles include intracellular transport in neurons, endosome and lysosome trafficking, spindle assembly and chromosome movements during mitosis and meiosis, and general organelle positioning.

Regulation of kinesin activity involves autoinhibition, cargo binding, and interactions with light chains, adaptors, and other proteins that control when and where they act. Dysfunction of kinesins is linked to neurodegenerative diseases, developmental defects, and cancer, and some kinesins are explored as targets for therapy. Research on kinesins employs structural approaches such as crystallography and cryo-electron microscopy, as well as single-molecule fluorescence to study their mechanics and regulation.