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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)

We studied the timing of mitotic loss of maternally and paternally derived chromosomes among the progeny of Drosophila melanogaster females homozygous for an amorphic mutation in ncd, a gene encoding a kinesin-like protein. In order to determine the division at which chromosome loss occurs, we estimated the fraction of XO nuclei resulting from X chromosome loss by scoring the phenotype of 47 adult cuticular landmarks in 160 XX-XO mosaics (gynandromorphs) derived from maternal X chromosome loss, and 33 gynandromorphs derived from paternal X chromosome loss. The results show that while most of the mitotic loss of maternally derived chromosomes occurs at the first cleavage division, the mitotic loss of paternally derived chromosomes occurs only at the second and later divisions. This means that paternally derived chromosomes are immune from the effects of ncd prior to karyogamy, which occurs after the first cleavage division. We discuss the implications of these results for the function of the ncd gene product and for other kinesin-like proteins in Drosophila.
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PMID:Timing of mitotic chromosome loss caused by the ncd mutation of Drosophila melanogaster. 139 61

Intracellular microtubule motor proteins may direct the motile properties and/or morphogenesis of the mitotic spindle (reviewed in ref. 3). The recent identification of kinesin-like proteins important for mitosis or meiosis indicates that kinesin-related proteins may play a universal role in eukaryotic cell division, but the precise function of such proteins in mitosis remains unknown. Here we use an in vitro assay for spindle assembly, derived from Xenopus egg extracts, to investigate the role of Eg5, a kinesin-like protein in Xenopus eggs. Eg5 is localized along spindle microtubules, and particularly enriched near spindle poles. Immunodepletion of Eg5 from egg extracts markedly reduces the extent of spindle formation in extracts, as does direct addition of anti-Eg5 antibodies. We also demonstrate that Eg5 is a plus-end-directed microtubule motor in vitro. Our results suggest a novel mechanism for the dynamic self-organization of spindle poles in mitosis.
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PMID:Mitotic spindle organization by a plus-end-directed microtubule motor. 140 65

To understand the interactions between the microtubule-based motor protein kinesin and intracellular components, we have expressed the kinesin heavy chain and its different domains in CV-1 monkey kidney epithelial cells and examined their distributions by immunofluorescence microscopy. For this study, we cloned and sequenced cDNAs encoding a kinesin heavy chain from a human placental library. The human kinesin heavy chain exhibits a high level of sequence identity to the previously cloned invertebrate kinesin heavy chains; homologies between the COOH-terminal domain of human and invertebrate kinesins and the nonmotor domain of the Aspergillus kinesin-like protein bimC were also found. The gene encoding the human kinesin heavy chain also contains a small upstream open reading frame in a G-C rich 5' untranslated region, features that are associated with translational regulation in certain mRNAs. After transient expression in CV-1 cells, the kinesin heavy chain showed both a diffuse distribution and a filamentous staining pattern that coaligned with microtubules but not vimentin intermediate filaments. Altering the number and distribution of microtubules with taxol or nocodazole produced corresponding changes in the localization of the expressed kinesin heavy chain. The expressed NH2-terminal motor and the COOH-terminal tail domains, but not the alpha-helical coiled coil rod domain, also colocalized with microtubules. The finding that both the kinesin motor and tail domains can interact with cytoplasmic microtubules raises the possibility that kinesin could crossbridge and induce sliding between microtubules under certain circumstances.
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PMID:Cloning and expression of a human kinesin heavy chain gene: interaction of the COOH-terminal domain with cytoplasmic microtubules in transfected CV-1 cells. 160 88

Mature Drosophila oocytes are arrested in metaphase of the first meiotic division. We have examined microtubule and chromatin reorganization as the meiosis I spindle assembles on maturation using indirect immunofluorescence and laser scanning confocal microscopy. The results suggest that chromatin captures or nucleates microtubules, and that these subsequently form a highly tapered spindle in which the majority of microtubules do not terminate at the poles. Nonexchange homologs separate from each other and move toward opposite poles during spindle assembly. By the time of metaphase arrest, these chromosomes are positioned on opposite half spindles, between the metaphase plate and the spindle poles, with the large nonexchange X chromosomes always closer to the metaphase plate than the smaller nonexchange fourth chromosomes. Nonexchange homologs are therefore oriented on the spindle in the absence of a direct physical linkage, and the spindle position of these chromosomes appears to be determined by size. Loss-of-function mutations at the nod locus, which encodes a kinesin-like protein, cause meiotic loss and nondisjunction of nonexchange chromosomes, but have little or no effect on exchange chromosome segregation. In oocytes lacking functional nod protein, most of the nonexchange chromosomes are ejected from the main chromosomal mass shortly after the nuclear envelope breaks down and microtubules interact with the chromatin. In addition, the nonexchange chromosomes that are associated with spindles in nod/nod oocytes show excessive poleward migration. Based on these observations, and the structural similarity of the nod protein and kinesin, we propose that nonexchange chromosomes are maintained on the half spindle by opposing poleward and anti-poleward forces, and that the nod protein provides the anti-poleward force.
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PMID:Meiotic spindle assembly in Drosophila females: behavior of nonexchange chromosomes and the effects of mutations in the nod kinesin-like protein. 174 Apr 71

Kinesin was previously immunolocalized to mitotic apparatuses (MAs) of early sea urchin blastomeres (Scholey, J.M., M.E. Porter, P.M. Grissom, and J.R. McIntosh. 1985. Nature [Lond.]. 318:483-486). Here we report evidence that this MA-associated motor protein is a conventional membrane-bound kinesin, rather than a kinesin-like protein. Our evidence includes the observation that the deduced amino acid sequence of this sea urchin kinesin heavy chain is characteristic of a conventional kinesin. In addition, immunolocalizations using antibodies that distinguish kinesin from kinesin-like proteins confirm that conventional kinesin is concentrated in MAs. Finally, our immunocytochemical data further suggest that conventional kinesin is associated with membranes which accumulate in MAs and interphase asters of early sea urchin embryos, and with vesicles that are distributed in the perinuclear region of coelomocytes. Thus kinesin may function as a microtubule-based vesicle motor in some MAs, as well as in the interphase cytoplasm.
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PMID:Subcellular localization and sequence of sea urchin kinesin heavy chain: evidence for its association with membranes in the mitotic apparatus and interphase cytoplasm. 182 46

The KAR3 gene is essential for yeast nuclear fusion during mating, and its expression is strongly induced by alpha factor. The predicted KAR3 protein sequence contains two globular domains separated by an alpha-helical coiled coil. The carboxy-terminal domain is homologous to the amino-terminal mechanochemical domain of Drosophila kinesin heavy chain. Mutation of the putative ATP binding site produces a dominant "poison" of nuclear fusion. The mutant protein shows enhanced microtubule association in vivo, as predicted for a kinesin-like protein in a state of rigor binding. Localization of hybrid proteins to cytoplasmic microtubules in shmoos indicates that the amino-terminal domain also contains determinants for microtubule association. Thus, KAR3 is a member of a larger family of kinesin-like proteins characterized by the presence of the mechanochemical domain tethered to different protein binding domains. The phenotypes of kar3 mutants suggest that the protein mediates microtubule sliding during nuclear fusion and possibly mitosis.
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PMID:KAR3, a kinesin-related gene required for yeast nuclear fusion. 213 12

We identified and sequenced a cDNA clone encoding a kinesin-like protein from Drosophila. The predicted product of this cDNA has a carboxy-terminal domain that is substantially similar to the motor domain of kinesin heavy chain. The amino-terminal domain is unlike that found in previously identified kinesins or kinesin-like proteins. Analyses of this new sequence suggest that the maximal motor unit in the kinesin superfamily may be as little as 350 amino acids, and that the existence of both kinesin and kinesin-like molecules must be an evolutionarily ancient feature of eukaryotes. We also tested some of the biochemical properties of the protein encoded by this cDNA and found them to be similar to those of kinesin. Finally, the clone we isolated appears to correspond to the non-claret disjunctional (ncd) gene, which when mutant causes defects in meiotic and early embryonic mitotic chromosome segregation, and whose recently determined sequence predicts a kinesin-like domain.
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PMID:Identification and characterization of a gene encoding a kinesin-like protein in Drosophila. 214 Sep 58

To understand the molecular basis of microtubule-associated motility during mitosis, the mechanochemical factors that generate the relevant motile force must be identified. Myosin, the ATPase that interacts with actin to produce the force for muscle contraction and other forms of cell motility, is believed to be involved in cytokinesis but not in mitosis. Dynein, the mechanochemical enzyme that drives microtubule sliding in eukaryotic cilia and flagella, has been identified in the cytoplasm of sea urchin eggs, but the evidence that it is involved in cytoplasmic microtubule-based motility (rather than serving as a precursor for embryonic cilia) is equivocal. Microtubule-associated ATPases have been prepared from other tissues, but their role in cytoplasmic motility is also unknown. Recent work on axoplasmic transport, however, has led to the identification of a novel mechanochemical protein called kinesin, which is thought to generate the force for moving vesicles along axonal microtubules. These results suggest that kinesin may also be a mechanochemical factor for non-axoplasmic forms of microtubule-based motility, such as mitosis. We describe here the identification and isolation of a kinesin-like protein from the cytoplasm of sea urchin eggs. We present evidence that this protein is localized in the mitotic spindle, and propose that it may be a mechanochemical factor for some form of motility associated with the mitotic spindle.
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PMID:Identification of kinesin in sea urchin eggs, and evidence for its localization in the mitotic spindle. 293 90

The isozyme form of eukaryotic initiation factor 4F [eIF-(iso)4F] from wheat germ is composed of a p28 subunit that binds the 7-methylguanine cap of mRNA and a p86 subunit having unknown function. The p86 subunit was found to have limited sequence similarity to a kinesin-like protein encoded by the katA gene of Arabidopsis thaliana. Native wheat germ eIF-(iso)4F and bacterially expressed p86 subunit and p86-p28 complex bound to taxol-stabilized maize microtubules (MTs) in vitro. Binding saturation occurred at 1 mol of p86 per 5-6 mol of polymerized tubulin dimer, demonstrating a substoichiometric interaction of p86 with MTs. No evidence was found for a direct interaction of the p28 subunit with MTs. Unlike kinesin, cosedimentation of eIF-(iso)4F with MTs was neither reduced by MgATP nor enhanced by adenosine 5'-[gamma-imido]triphosphate. Both p86 subunit and p86-p28 complex induced the bundling of MTs in vitro. The p86 subunit was immunolocalized to the cytosol in root maize cells and existed in three forms: fine particles, coarse particles, and linear patches. Many coarse particles and linear patches were colocalized or closely associated with cortical MT bundles in interphase cells. The results indicate that the p86 subunit of eIF-(iso)4F is a MT-associated protein that may simultaneously link the translational machinery to the cytoskeleton and regulate MT disposition in plant cells.
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PMID:Function of the p86 subunit of eukaryotic initiation factor (iso)4F as a microtubule-associated protein in plant cells. 762 81

We have isolated a 1224 bp cDNA clone from a Bombyx mori embryonic cDNA library which contains sequences homologous to the kinesin-like protein gene, ncd, which is required for distribution of chromosomes at meiosis in Drosophila melanogaster females. This clone includes both a microtubule motor and the ATP-binding domains found in kinesin-like proteins. The motor domain is classified in the group of the BimC and cut7, which have a role in spindle formation during mitosis of Aspergillus nidulans and Schizosaccharomyces pombe, respectively. However, the location of the domain at the carboxy terminus is not common in this family, except for ncd and KAR3.
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PMID:cDNA structure and characterization of a kinesin-like protein from the silkworm Bombyx mori. 770 3


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