Microtubule minus end

Fan, J., Griffiths, A., Lockhart, D. A., Cross, R. A., and Amos, L. A. (1996). Microtubule minus ends can be labelled with a phage display antibody specific to alpha-tubulin. / Mol. Biol. 259, 325-330. 

Wiese C, Zheng Y. 2000. A new function for the gamma-tubulin ring complex as a microtubule minus-end cap. Nat. Cell Biol. 2 358-64... 

Because all tubulin dimers in a microtubule are oriented similarly, microtubules are polar structures. The end of the microtubule at which growth occurs is the plus end, and the other is the minus end. Microtubules in vitro carry out a GTP-dependent process called treadmiUing, in which tubulin dimers are added to the plus end at about the same rate at which dimers are removed from the minus end (Figure 17.3). 

MTs are stabilized at their minus ends by the centrosome (also called microtubule organizing center, MTOC). Centrosomes are protein complexes containing among other proteins two centrioles (ringlike structures) and a-tubulin. Centrosomes serve as nucleation points for microtubular polymerization and constrain the lattice structure of an MT to 13 protofila-... 

A microtubule is a hollow tube of 25 nm diameter formed by 13 protofilaments. Each protofilament consists of polymerized a- and (3-tubulin heterodimers. Microtubules are polarized and have a plus and a minus end. 

Motor proteins move along microtubules or F-actin. The respective motor domains are linked to their cargoes via adaptor proteins. Kinesin motors move only to the plus and dynein motors only to the minus ends of microtubules. Myosin motors move along F-actin. When motors are immobilized at their cargo binding area, they can move microtubules or F-actin, respectively. 

Goncgy One of the popular models to explain the 90° rotation of centrosomes in PI invokes capture of astral microtubules at an anterior cortical site by a localized minus-end directed motor. This would generate a torque on the centrosome/ nuclear complex and reel one of the centrosomes in the direction of the cortical site (Hyman 1989). 

The cytoskeleton appears to have a significant role in the localization of different organelles, as well as in the active transport of vesicles (see Chs 8 and 28). Both microtubules (MTs) and actin filaments appear to be involved in these processes. For example, through its association with the minus end of MTs, the Golgi apparatus is... 

Cytoplasmic dyneins may have multiple roles in the neuron. The identification of kinesin as a plus-end directed microtubule motor suggested that it is involved in anterograde transport but left the identity of the retrograde motor an open question. Since flagellar dynein was known to be a minus-end-directed motor, interest in cytoplasmic dyneins was renewed. Identification of the cytoplasmic form of dynein in nervous tissue came as an indirect result of the discovery of kinesin. 

With regard to microtubular ultrastructure, micro filaments (5-7 run in diameter) are composed of filamentous actin. The tubule-like structures are formed by a, P-tubulin heterodimers. The wall is composed of 13 parallel protofilaments. Various microtubule-associated proteins and motor proteins (kinesin and dynein) are bound to the wall. The microtubule is a polar structure, i.e., plus and minus ends. 

The reattachment of two supramolecular polymers, such as that observed when a high concentration of sheared microtubules is permitted to incubate in vitro. End-to-end annealing of microtubules is an unlikely process in living cells, because (a) the viscosity of the cytoplasm is apt to reduce greatly the tumbling of these polymers and (b) the so-called minus ends of the microtubules are usually firmly attached to microtubule-organizing centers. 

With respect to a solvent, the overall solvation capability for solutes. 2. A property of bodies or systems that have a distinct direction i.e., that have different or opposing physical properties or characteristics at different points. For example, an amino acid sequence in a polypeptide has polarity in that there is an amino end and a carboxyl end of the sequence. Similarly, microtubules and actin filaments have plus (+)-ends and minus (-)-ends that establish directionality for cellular and intracellular locomotion. 3. The state in which there is either a positive or negative aspect relative to the two poles of a magnet or to electrification. 4. Attraction toward an object or attraction in a specific direction. 5. In mathematics, the positive or negative sign of numbers. 

Suomalainen, M., Nakano, M.Y., Keller, S., Boucke, K., Stidwill, R.P. and Greber, U.F. (1999) Microtubule-dependent plus- and minus end-directed motilities are competing processes for nuclear targeting of adenovirus. J. Cell Biol, 144, 657-672. 

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