Kinesiini

Kinesiini, known in English as kinesins, are a family of microtubule-based motor proteins that transport cargo inside eukaryotic cells. They convert chemical energy from ATP hydrolysis into mechanical work, enabling directed movement along microtubules. Most kinesins are dimeric, with two motor domains that bind to microtubules, a coiled-coil stalk that dimerizes the protein, and a tail region that attaches to cargo via adaptor proteins. In the majority of kinesins, movement is toward the microtubule plus end, supporting anterograde transport.

Kinesins generate motion through a chemomechanical cycle in which ATP binding, hydrolysis, and product release regulate microtubule affinity. The two motor heads coordinate to produce processive, hand-over-hand stepping with typical steps of about 8 nanometers. The speed and run length vary among kinesin family members. There are exceptions, such as kinesin-14 motors, which have a reverse architecture with the motor domain at the C-terminus and can move toward the microtubule minus end.

Kinesins perform essential cellular functions, including transport of vesicles, mitochondria, and mRNA, and they support the distribution of synaptic components in neurons. They also contribute to mitosis and meiosis by organizing and moving spindle apparatus and chromosomes. Specialized motors regulate microtubule dynamics during cell division, such as kinesin-5, which slides antiparallel microtubules, and kinesin-13, which promotes depolymerization.

In humans, kinesins comprise a large superfamily (KIF genes) with more than 40 members encoded. Dysfunctions in kinesin-based transport are linked to neurodegenerative diseases and neuropathies, while some kinesins are targeted by cancer therapies to disrupt mitotic progression. The name kinesin derives from kinesis, the Greek word for movement.