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)

Synapsin I plays an important role in the regulation of neurotransmitter release, since it binds to synaptic vesicles and to the cytoskeleton, and it bundles F-actin and microtubules. We have previously shown by tryptic digestion of synapsin I that a 44 kDa fragment contains a binding site for polymerized tubulin. In the present experiments, we test whether synapsin I and microtubule-associated proteins (MAPs) have the same or a different binding site on tubulin molecules. Our results show that heat stable MAPs do not compete with synapsin I for binding to taxol tubulin. In addition, subtilisin digestion of tubulin, which suppresses MAPs binding, does not abolish synapsin I cosedimentation with taxol tubulin. Thus, our results strongly suggest that synapsin I (as reported for kinesin) does not bind to the 4 kDa subtilisin digested C-terminal part of the tubulin molecule.
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PMID:Do synapsin I and microtubule-associated proteins bind to a common site on polymerized tubulin? 212 53

It has been previously shown that a class of microtubule proteins, the so-called microtubule-associated proteins (MAPs), binds to the C-terminal part of tubulin subunits. We show here that microtubules composed of tubulin whose 4-kDa C-terminal domain was cleaved by subtilisin (S-microtubules) are unable to bind MAPs but can still bind the anterograde translocator protein kinesin and the retrograde translocator dynein. Binding of both motors to S-microtubules, like their binding to normal microtubules, was ATP-dependent. In addition, direct competition experiments showed that binding sites for kiensin and MAPs on the microtubule surface lattice do not overlap. Furthermore, S-microtubules stimulated the ATPase activity of kinesin at least 8-fold, and the affinities of kinesin for control and S-microtubules were identical. S-microtubules were able to glide along kinesin-coated coverslips at a rate of 0.2 microns/s, the same rate as control microtubules. We conclude, that unlike MAPs, kinesin and cytoplasmic dynein bind to the tubulin molecule outside the C-terminal region.
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PMID:Microtubule-associated proteins and microtubule-based translocators have different binding sites on tubulin molecule. 213 10

Kinesin is a microtubule-activated, mechanochemical ATPase capable of moving particles along microtubules and making microtubules glide along a solid substrate. In this study we used limited proteolysis to study the structure of bovine brain kinesin, a heterotetramer composed of two heavy (120-kDa) and two light (62-kDa) chains. alpha-chymotrypsin, trypsin, and subtilisin all produced a protease-resistant 45-kDa fragment from the kinesin heavy chain. As isolated by gel-filtration chromatography, this fragment contains both the microtubule-binding site and the ATP catalytic site of the molecule. Proteolytic cleavage stimulated microtubule-dependent Mg2+-ATPase activity 4- to 5-fold up to 75-120 mumol ATP/min/mg. Cleavage also increased the affinity of the fragment for microtubules at least 10-fold. Since the purified fragment does not support the gliding of flagellar axonemes, we propose that cleavage of the heavy chain uncouples ATPase activity from its translocator activity, which may require other parts of the molecule.
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PMID:Isolation of a 45-kDa fragment from the kinesin heavy chain with enhanced ATPase and microtubule-binding activities. 252 Dec 21

We have used a fluorescent derivative of kinesin, AF-kinesin (kinesin conjugated with 5-(iodoacetamido)fluorescein), to investigate the binding site of kinesin on microtubules and to compare this site with that to which tau binds. Microtubules saturated with tau will bind AF-kinesin in the presence of the ATP analogue, 5'-[beta,gamma-imino]triphosphate (AdoPP[NH]P). This shows that there are distinct binding sites for the two proteins. Further evidence comes from digestion studies where taxol-stabilised microtubules were treated with subtilisin, resulting in the cleavage of C-terminal residues from both the alpha- and beta-tubulin subunits. These treated microtubules can no longer bind tau, but are able to bind AF-kinesin in the presence of AdoPP[NH]P. Finally, AF-kinesin will support the gliding of subtilisin-digested microtubules in the presence of ATP at rates comparable to those obtained with non-digested microtubules. These results show directly that the binding site for kinesin is outside the C-terminal region of tubulin that is removed by subtilisin and is distinct from the binding site of tau.
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PMID:Kinesin and tau bind to distinct sites on microtubules. 790 14

In neuronal cells, microtubule-associated proteins (MAPs) can be classified into two distinct groups. One consists of force-producing MAPs, the main components of which are kinesin and cytoplasmic dynein. The other is composed of fibrous MAPs, which include tau and MAP2. Many studies have been performed on the respective groups to understand their structures and functions. However, the problem of how the groups interact with each other on microtubules is still unresolved. To elucidate the interaction between kinesin or cytoplasmic dynein and tau or MAP2, we performed three experiments: competition, motility assay, and cosedimentation. To distinguish whether the binding competition is caused by steric hindrance of the projection domains of MAPs or by the competition of the binding sites on microtubules, we used microtubule binding domains of tau and MAP2 as well as native proteins. Our results revealed that kinesin or cytoplasmic dynein and tau or MAP2 complete for almost the same binding domains located on the carboxyl-terminal side of alpha- and the amino-terminal side of beta-tubulin from the site of subtilisin cleavage. Furthermore, the projection of tau, and probably of MAP2, might inhibit the binding of kinesin or cytoplasmic dynein to microtubules by steric hindrance. These findings will provide a useful step toward understanding the regulation system of intracellular organelle transport.
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PMID:Competition between motor molecules (kinesin and cytoplasmic dynein) and fibrous microtubule-associated proteins in binding to microtubules. 810 2

Kinesin is a mechanoenzyme that couples adenosine triphosphate hydrolysis to the generation of force and movement along microtubules. To gain insight into the interactions of kinesin and microtubules, cross-linking, mapping, and proteolysis experiments were executed. The motor domain of kinesin was consistently cross-linked to both alpha- and beta-tubulin subunits. Initial mapping of the cross-linked kinesin suggested that amino acids within the N- and C-terminal cyanogen bromide fragments of the motor domain formed cross-links to both alpha- and beta-tubulin subunits. Mapping of the cross-linked tubulin suggested that cross-linking to kinesin motors occurred within the negatively charged, C-terminal cyanogen bromide fragments of alpha- and beta-tubulin subunits. Treatment of microtubules with subtilisin, a protease that cleaves C-terminal fragments from alpha- and beta-tubulin, reduced their ability to be cross-linked to kinesin motors supporting the idea that C-terminal sequences of alpha- and beta-tubulin may interact with kinesin motors. Finally, of three synthetic peptides, a peptide consisting of the last 12 C-terminal amino acids of beta-tubulin competitively interfered with the microtubule-stimulated adenosine triphosphatase activity of the kinesin motor, further suggesting that C-terminal sequences of beta-tubulin may be involved in kinesin binding.
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PMID:Probing the kinesin-microtubule interaction. 908 88

Calponin is a basic smooth muscle protein capable of binding to actin, calmodulin, tropomyosin, and phospholipids. We have found that the basic calponin interacted with brain tubulin under polymerized and unpolymerized conditions in vitro [Fujii, T., Hiromori, T., Hamamoto, M., and Suzuki, T. (1997) J. Biochem. 122, 344-351]. We examined the calponin-binding site on the tubulin molecule by sedimentation, limited digestion, chemical-cross linking, immunoblotting, and delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometric (DE MALDI-TOF) analyses. Calponin interacts with both the alpha and beta tubulins and only slightly with the tyrosinated and acetylated form of alpha tubulin. The binding of calponin to microtubules was blocked by adding poly(L-aspartic acid) (PLAA) or MAP2. After digestion of microtubule proteins with subtilisin, the amount of calponin binding to alphabetas microtubules was reduced compared to native microtubules, but no further reduction was observed in the case of alphasbetas microtubules. The chemical cross-linked products of calponin and synthesized peptides (KDYEEVGVDSVEGE; alpha-KE) derived from the C-terminal region of alpha tubulin and (YQQYQDATADEQG; beta-YG) and (GEFEEEGEEDEA; beta-GA) from that of beta tubulin were detected by mass spectrometry. One kind of calponin-peptide complex was formed in the presence of alpha-KE or beta-YG, while five complexes (calponin:peptide = 1:1-5) were generated in the presence of beta-GA. Peptides alpha-KE and beta-GA inhibited the binding of calponin to tubulin produced by EDC in a concentration-dependent manner. These findings suggest that basic calponin interacts with both tubulin subunits and that their C-terminal regions, which also contain the binding sites of MAP2, tau, and kinesin, may be involved in calponin-binding.
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PMID:Identification of the binding region of basic calponin on alpha and beta tubulins. 1022 May 77

In motor movement on microtubules, the anionic C-terminal of tubulin has been implicated as a significant factor. Our digital analyses of movements of cytoplasmic dynein- and kinesin-coated beads on microtubules have revealed dramatic changes when the C-terminal region (2-4-kDa fragment) of tubulin was cleaved by limited subtilisin digestion of assembled microtubules. For both motors, bead binding to microtubules was decreased threefold, bead run length was decreased over fourfold, and there was a dramatic 20-fold decrease in diffusional movements of cytoplasmic dynein beads on microtubules (even with low motor concentrations where the level of bead motile activity was linear with motor concentration). The velocity of active bead movements on microtubules was unchanged for cytoplasmic dynein and slightly decreased for kinesin. There was also a decrease in the frequency of bead movements without a change in velocity when the ionic strength was raised. However, with high ionic strength there was not a decrease in run length or any selective inhibition of the diffusional movement. The C-terminal region of tubulin increased motor run length (processivity) by inhibiting "detachment" but without affecting velocity. Because the major motor binding sites of microtubules are not on the C-terminal tail of tubulin (), we suggest that the changes are the result of the compromise of a weakly attached state that is the lowest affinity step in both motors' ATPase cycles and is not rate limiting.
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PMID:The C-terminus of tubulin increases cytoplasmic dynein and kinesin processivity. 1073 74

The neck region of kinesin constitutes a key component in the enzyme's walking mechanism. Here we applied cryoelectron microscopy and image reconstruction to investigate the location of the kinesin neck in dimeric and monomeric constructs complexed to microtubules. To this end we enhanced the visibility of this region by engineering an SH3 domain into the transition between neck linker and neck coiled coil. The resulting chimeric kinesin constructs remained functional as verified by physiology assays. In the presence of AMP-PNP the SH3 domains allowed us to identify the position of the neck in a well defined conformation and revealed its high flexibility in the absence of nucleotide. We show here the double-headed binding of dimeric kinesin along the same protofilament, which is characterized by the opposite directionality of neck linkers. In this configuration the neck coiled coil appears fully zipped. The position of the neck region in dimeric constructs is not affected by the presence of the tubulin C-termini as confirmed by subtilisin treatment of microtubules prior to motor decoration.
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PMID:Nucleotide-induced conformations in the neck region of dimeric kinesin. 1266 Jan 59

The flexible tubulin C-terminal tails (CTTs) have recently been implicated in the walking mechanism of dynein and kinesin. To address their role in the case of conventional kinesin, we examined the structure of kinesin-microtubule (MT) complexes before and after CTT cleavage by subtilisin. Our results show that the CTTs directly modulate the motor-tubulin interface and the binding properties of motors. CTT cleavage increases motor binding stability, and kinesin appears to adopt a binding conformation close to the nucleotide-free configuration under most nucleotide conditions. Moreover, C-terminal cleavage results in trapping a transient motor-ADP-MT intermediate. Using SH3-tagged dimeric and monomeric constructs, we could also show that the position of the kinesin neck is not affected by the C-terminal segments of tubulin. Overall, our study reveals that the tubulin C-termini define the stability of the MT-kinesin complex in a nucleotide-dependent manner, and highlights the involvement of tubulin in the regulation of weak and strong kinesin binding states.
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PMID:Modulation of kinesin binding by the C-termini of tubulin. 1497 55


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