Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.4.4 (kinesin)
5,033 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The highly dynamic process of cell division is effected, in part, by molecular motors that generate the forces necessary for its enactment. Several members of the kinesin superfamily of motor proteins are implicated in mitosis, such as CENP-E, which plays essential roles in cell division, including association with the kinetochore to stabilize attachment of chromosomes to microtubules prior to and during their separation. Neither the functional assembly state of CENP-E nor its direction of motion along the polar microtubule are certain. To determine the mode of interaction between CENP-E and microtubules, we have used cryo-electron microscopy to visualize CENP-E motor domains complexed with microtubules and calculated a density map of the complex to 17 A resolution by combining helical and single-particle reconstruction methods. The interface between the motor domain and microtubules was modeled by docking atomic-resolution models of the subunits into the cryoEM density map. Our results support a plus end motion for CENP-E, consistent with features of the crystallographic structure. Despite considerable functional differences from the monomeric transporter kinesin KIF1A and the oppositely directed ncd kinesin, CENP-E appears to share many features of the intermolecular interactions, suggesting that differences in motor function are governed by small variations in the loops at the microtubule interface.
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PMID:Human kinetochore-associated kinesin CENP-E visualized at 17 A resolution bound to microtubules. 1692 26

Kinesin is an ATP-driven microtubule (MT)-based motor fundamental to organelle transport. Although a number of kinesin crystal structures have been solved, the structural evidence for coupling between the bound nucleotide and the conformation of kinesin is elusive. In addition, the structural basis of the MT-induced ATPase activity of kinesin is not clear because of the absence of the MT in the structure. Here, we report cryo-electron microscopy structures of the monomeric kinesin KIF1A-MT complex in two nucleotide states at about 10 A resolution, sufficient to reveal the secondary structure. These high-resolution maps visualized clear structural changes that suggest a mechanical pathway from the nucleotide to the neck linker via the motor core rotation. In addition, new nucleotide binding pocket conformations are observed that are different from X-ray crystallographic structures; it is closed in the 5'-adenylyl-imidodiphosphate state, but open in the ADP state. These results suggest a structural model of biased diffusion movement of monomeric kinesin motor.
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PMID:High-resolution cryo-EM maps show the nucleotide binding pocket of KIF1A in open and closed conformations. 1694 6

A novel equality relating the rate of energy dissipation to a degree of violation of the fluctuation-response relation (FRR) in non-equilibrium Langevin systems is described. The FRR is a relation between the correlation function of the fluctuations and the response function of macroscopic variables. Although it has been established that the FRR holds in equilibrium, physical significance of violation of the FRR in non-equilibrium systems has been under debate. Recently, the authors have found that an extent of the FRR violation is related in a simple equality to the rate of energy dissipation into the environment in non-equilibrium Langevin systems. In this paper, we fully explain the FRR, the FRR violation, and the new equality with regard to a Langevin model termed a Brownian motor model, which is considered as a simple model of a biological molecular motor. Furthermore, applications of our result to experimental studies of molecular motors are discussed, and, as an illustration, we predict the value of a new time constant regarding the motion of a KIF1A, which is a kind of single-headed kinesin.
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PMID:Fluctuations, responses and energetics of molecular motors. 1730 91

Microtubules function as molecular tracks along which motor proteins transport a variety of cargo to discrete destinations within the cell. The carboxyl termini of alpha- and beta-tubulin can undergo different posttranslational modifications, including polyglutamylation, which is particularly abundant within the mammalian nervous system. Thus, this modification could serve as a molecular "traffic sign" for motor proteins in neuronal cells. To investigate whether polyglutamylated alpha-tubulin could perform this function, we analyzed ROSA22 mice that lack functional PGs1, a subunit of alpha-tubulin-selective polyglutamylase. In wild-type mice, polyglutamylated alpha-tubulin is abundant in both axonal and dendritic neurites. ROSA22 mutants display a striking loss of polyglutamylated alpha-tubulin within neurons, including their neurites, which is associated with decreased binding affinity of certain structural microtubule-associated proteins and motor proteins, including kinesins, to microtubules purified from ROSA22-mutant brain. Of the kinesins examined, KIF1A, a subfamily of kinesin-3, was less abundant in neurites from ROSA22 mutants in vitro and in vivo, whereas the distribution of KIF3A (kinesin-2) and KIF5 (kinesin-1) appeared unaltered. The density of synaptic vesicles, a cargo of KIF1A, was decreased in synaptic terminals in the CA1 region of hippocampus in ROSA22 mutants. Consistent with this finding, ROSA22 mutants displayed more rapid depletion of synaptic vesicles than wild-type littermates after high-frequency stimulation. These data provide evidence for a role of polyglutamylation of alpha-tubulin in vivo, as a molecular traffic sign for targeting of KIF1 kinesin required for continuous synaptic transmission.
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PMID:Loss of alpha-tubulin polyglutamylation in ROSA22 mice is associated with abnormal targeting of KIF1A and modulated synaptic function. 1736 Jun 31

In eukaryotic cells, many motor proteins can move simultaneously on a single microtubule track. This leads to interesting collective phenomena such as jamming. Recently we reported [Phys. Rev. Lett. 95, 118101 (2005)] a lattice-gas model which describes traffic of unconventional (single-headed) kinesins KIF1A. Here we generalize this model, introducing an interaction parameter c, to account for an interesting mechanochemical process. We have been able to extract all the parameters of the model, except c, from experimentally measured quantities. In contrast to earlier models of intracellular molecular motor traffic, our model assigns distinct "chemical" (or, conformational) states to each kinesin to account for the hydrolysis of adenosine triphosphate (ATP), the chemical fuel of the motor. Our model makes experimentally testable theoretical predictions. We determine the phase diagram of the model in planes spanned by experimentally controllable parameters, namely, the concentrations of kinesins and ATP. Furthermore, the phase-separated regime is studied in some detail using analytical methods and simulations to determine, e.g., the position of shocks. Comparison of our theoretical predictions with experimental results is expected to elucidate the nature of the mechanochemical process captured by the parameter c.
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PMID:Intracellular transport by single-headed kinesin KIF1A: effects of single-motor mechanochemistry and steric interactions. 1750 Sep 19

We develop a mixed elastic network model (MENM) to study large-scale conformational transitions of proteins between two (or more) known structures. Elastic network potentials for the beginning and end states of a transition are combined, in effect, by adding their respective partition functions. The resulting effective MENM energy function smoothly interpolates between the original surfaces, and retains the beginning and end structures as local minima. Saddle points, transition paths, potentials of mean force, and partition functions can be found efficiently by largely analytic methods. To characterize the protein motions during a conformational transition, we follow "transition paths" on the MENM surface that connect the beginning and end structures and are invariant to parameterizations of the model and the mathematical form of the mixing scheme. As illustrations of the general formalism, we study large-scale conformation changes of the motor proteins KIF1A kinesin and myosin II. We generate possible transition paths for these two proteins that reveal details of their conformational motions. The MENM formalism is computationally efficient and generally applicable even for large protein systems that undergo highly collective structural changes.
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PMID:Protein conformational transitions explored by mixed elastic network models. 1759 47

The processive movement of single-headed kinesins is studied by using a ratchet model of non-Markov process, which is built on the experimental evidence that the strong binding of kinesin to microtubule in rigor state induces a large apparent change in the local microtubule conformation. In the model, the microtubule plays a crucial active role in the kinesin movement, in contrast to the previous belief that the microtubule only acts as a passive track for the kinesin motility. The unidirectional movement of single-headed kinesin is resulted from the asymmetric periodic potential between kinesin and microtubule while its processivity is determined by its binding affinity for microtubule in the weak ADP state. Using the model, various experimental results for monomeric kinesin KIF1A, such as the mean step size, the step-size distribution, the long run length and the mean velocity versus load, can be well explained quantitatively. This local conformational change of the microtubule may also play important roles in the processive movement of conventional two-headed kinesins. An experiment to verify the model is suggested.
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PMID:Processivity of single-headed kinesin motors. 1797 15

Kinesin-3 motors drive the transport of synaptic vesicles and other membrane-bound organelles in neuronal cells. In the absence of cargo, kinesin motors are kept inactive to prevent motility and ATP hydrolysis. Current models state that the Kinesin-3 motor KIF1A is monomeric in the inactive state and that activation results from concentration-driven dimerization on the cargo membrane. To test this model, we have examined the activity and dimerization state of KIF1A. Unexpectedly, we found that both native and expressed proteins are dimeric in the inactive state. Thus, KIF1A motors are not activated by cargo-induced dimerization. Rather, we show that KIF1A motors are autoinhibited by two distinct inhibitory mechanisms, suggesting a simple model for activation of dimeric KIF1A motors by cargo binding. Successive truncations result in monomeric and dimeric motors that can undergo one-dimensional diffusion along the microtubule lattice. However, only dimeric motors undergo ATP-dependent processive motility. Thus, KIF1A may be uniquely suited to use both diffuse and processive motility to drive long-distance transport in neuronal cells.
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PMID:Mammalian Kinesin-3 motors are dimeric in vivo and move by processive motility upon release of autoinhibition. 1933 88

Resistance to chemotherapy remains a major barrier to the successful treatment of cancer. To understand mechanisms underlying docetaxel resistance in breast cancer, we used an insertional mutagenesis strategy to identify proteins whose overexpression confers resistance. A strong promoter was inserted approximately randomly into the genomes of tumor-derived breast cancer cells, using a novel lentiviral vector. We isolated a docetaxel-resistant clone in which the level of the kinesin KIFC3 was elevated. When KIFC3 or the additional kinesins KIFC1, KIF1A, or KIF5A were overexpressed in the breast cancer cell lines MDA-MB231 and MDA-MB 468, the cells became more resistant to docetaxel. The binding of kinesins to microtubules opposes the stabilizing effect of docetaxel that prevents cytokinesis and leads to apoptosis. Our finding that kinesins can mediate docetaxel resistance might lead to novel therapeutic approaches in which kinesin inhibitors are paired with taxanes.
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PMID:Overexpression of kinesins mediates docetaxel resistance in breast cancer cells. 1978 44

Cells generate diverse microtubule populations by polymerization of a common alpha/beta-tubulin building block. How microtubule associated proteins translate microtubule heterogeneity into specific cellular functions is not clear. We evaluated the ability of kinesin motors involved in vesicle transport to read microtubule heterogeneity by using single molecule imaging in live cells. We show that individual Kinesin-1 motors move preferentially on a subset of microtubules in COS cells, identified as the stable microtubules marked by post-translational modifications. In contrast, individual Kinesin-2 (KIF17) and Kinesin-3 (KIF1A) motors do not select subsets of microtubules. Surprisingly, KIF17 and KIF1A motors that overtake the plus ends of growing microtubules do not fall off but rather track with the growing tip. Selection of microtubule tracks restricts Kinesin-1 transport of VSVG vesicles to stable microtubules in COS cells whereas KIF17 transport of Kv1.5 vesicles is not restricted to specific microtubules in HL-1 myocytes. These results indicate that kinesin families can be distinguished by their ability to recognize microtubule heterogeneity. Furthermore, this property enables kinesin motors to segregate membrane trafficking events between stable and dynamic microtubule populations.
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PMID:Single molecule imaging reveals differences in microtubule track selection between Kinesin motors. 1982 65


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