Kinesin

A kinesin is a protein belonging to a class of motor proteins found in eukaryotic cells.

Kinesins move along microtubule (MT) filaments, and are powered by the hydrolysis of adenosine triphosphate (ATP) (thus kinesins are ATPases). The active movement of kinesins supports several cellular functions including mitosis, meiosis and transport of cellular cargo, such as in axonal transport. Most kinesins walk towards the positive end of a microtubule, which, in most cells, entails transporting cargo such as protein and membrane components from the centre of the cell towards the periphery. This form of transport is known as anterograde transport. In contrast, dyneins are motor proteins that move toward the microtubules' negative end.

The kinesins

Kinesins were discovered as MT-based anterograde intracellular transport motors. The founding member of this superfamily, kinesin-1, was isolated as a heterotetrameric fast axonal organelle transport motor consisting of 2 identical motor subunits (KHC) and 2 "light chains" (KLC) via microtubule affinity purification from neuronal cell extracts. Subsequently a different, heterotrimeric plus-end-directed MT-based motor named kinesin-2, consisting of 2 distinct KHC-related motor subunits and an accessory "KAP" subunit, was purified from echinoderm egg/embryo extracts and is best known for its role in transporting protein complexes (IFT particles) along axonemes during cilium biogenesis. Molecular genetic and genomic approaches have led to the recognition that the kinesins form a diverse superfamily of motors that are responsible for multiple intracellular motility events in eukaryotic cells. For example, the genomes of mammals encode more than 40 kinesin proteins, organized into at least 14 families named kinesin-1 through kinesin-14.

Kinesin 8

The Kinesin 8 Family are a subfamily of the molecular motor proteins known as kinesins. Most kinesins transport materials or cargo around the cell while traversing along microtubule polymer tracks with the help of ATP-hydrolysis-created energy. The Kinesin 8 family has been shown to play an important role in chromosome alignment during mitosis. Kinesin 8 family members KIF18A in humans and Kip3 in yeast have been shown to be in vivo plus-end directed microtubule depolymerizers. During prometaphase of mitosis, the microtubules attach to the kinetochores of sister chromatids. Kinesin 8 is thought to play some role in this process, as knockdown of this protein via siRNA produces a phenotype of sister chromatids that are unable to align properly (see External Links).

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Kinesin family member 11

Kinesin-5 is a molecular motor protein that is essential in mitosis. Kinesin-5 proteins are members of kinesin superfamily, which are nanomotors that move along microtubule tracks in the cell. Named from studies in the early days of discovery, it is also known as kinesin family member 11, encoded by the KIF11 gene, or as BimC, Eg5 or N-2, based on the founding members of this kinesin family. The term kinesin-5 has been recommended based on a standardized nomenclature adopted by the scientific community.

Currently, there are over 70 different eukaryotic kinesin-5 proteins identified by sequence similarity. Members of this protein family are known to be involved in various kinds of spindle dynamics and essential for mitosis. The function of this gene product includes chromosome positioning, centrosome separation and establishing a bipolar spindle during cell mitosis. The human Kinesin-5 protein has been actively studied for its role in mitosis and its potential as a therapeutic target for cancer treatment.