Kinesin
Kinesin refers to a group of motor proteins in eukaryotic cells . In cooperation with other motor proteins such as myosin and dynein , they are essential for the intracellular transport of biological loads such as B. biomacromolecules, vesicles and cell organelles involved. Kinesin occurs together with dynein on microtubule filaments (part of the cytoskeleton ) as a transporter of vesicles and other molecules.
Layout and function
The kinesin complex consists of two heavy protein chains and two light protein chains. The kinesin protein itself consists of a head region, which can bind to microtubules and contains the catalytic domain, a neck, a long stem and a tail part that can interact with other proteins via a variety of connecting proteins. The energy for the transport is obtained from the cleavage of adenosine triphosphate (ATP) at the catalytic center of the head region. ATP hydrolysis at the active site changes the conformation of the head and neck, followed by an 8 nm step over a tubulin heterodimer , the structural unit of a microtubule. Kinesine complexes bind a molecule to be transported to themselves and then 'run' along a microtubule . They move processively, i.e. H. very stably bound to the microtubules, since one of the two heads is always bound to the microtubules. The transport is directed, most kinesins migrate on the microtubule in the direction of the growing microtubule end (so-called plus end).
Since microtubules usually grow from the inside of the cell to the outside, these kinesins transport their cargo from the inside of the cell to the cell periphery (anterograde transport). But there are also other kinesins (e.g. kinesin-like proteins ) that transport cargo towards the minus end. The transport on the microtubule towards the minus end is also carried out by dynein .
Web links
- The Inner Life of the Cell - Motor-Protein in Action (end of the first half of the animation )
- Jennifer McDowall / Interpro: Protein Of The Month: Kinesin. (engl.)
- Kinesin - An Introduction