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 flagella of the biflagellate unicellular alga Chlamydomonas have long been known to contain the microtubule-dependent motor protein dynein, but recent findings indicate they also contain multiple members of the kinesin superfamily. Two of these kinesin-like proteins are restricted to a single central-pair microtubule, raising the question of how proteins are targeted to specific microtubules within the flagellum. The kinesin-like proteins on the central-pair microtubules may cause the central-pair apparatus to rotate or twist during flagellar beating. Other kinesins within the flagellum may participate in movements associated with the flagellar membrane.
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PMID:Kinesin-like proteins in the flagella of Chlamydomonas. 1473 62

KAP is the non-motor subunit of the heteromeric plus-end directed microtubule (MT) motor protein kinesin-II essential for normal cilia formation. Studies in Chlamydomonas have demonstrated that kinesin-II drives the anterograde intraflagellar transport (IFT) of protein complexes along ciliary axonemes. We used a green fluorescent protein (GFP) chimera of KAP, KAP-GFP, to monitor movements of this kinesin-II subunit in cells of sea urchin blastulae where cilia are retracted and rebuilt with each mitosis. As expected if involved in IFT, KAP-GFP localized to apical cytoplasm, basal bodies, and cilia and became concentrated on basal bodies of newly forming cilia. Surprisingly, after ciliary retraction early in mitosis, KAP-GFP moved into nuclei before nuclear envelope breakdown, was again present in nuclei after nuclear envelope reformation, and only decreased in nuclei as ciliogenesis reinitiated. Nuclear transport of KAP-GFP could be due to a putative nuclear localization signal and nuclear export signals identified in the sea urchin KAP primary sequence. Our observation of a protein involved in IFT being imported into the nucleus after ciliary retraction and again after nuclear envelope reformation suggests KAP115 may serve as a signal to the nucleus to reinitiate cilia formation during sea urchin development.
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PMID:Redistribution of the kinesin-II subunit KAP from cilia to nuclei during the mitotic and ciliogenic cycles in sea urchin embryos. 1535 88

Chlamydomonas reinhardtii controls flagellar assembly such that flagella are of an equal and predetermined length. Previous studies demonstrated that lithium, an inhibitor of glycogen synthase kinase 3 (GSK3), induced flagellar elongation, suggesting that a lithium-sensitive signal transduction pathway regulated flagellar length (S. Nakamura, H. Takino, and M. K. Kojima, Cell Struct. Funct. 12:369-374, 1987). Here, we demonstrate that lithium treatment depletes the pool of flagellar proteins from the cell body and that the heterotrimeric kinesin Fla10p accumulates in flagella. We identify GSK3 in Chlamydomonas and demonstrate that its kinase activity is inhibited by lithium in vitro. The tyrosine-phosphorylated, active form of GSK3 was enriched in flagella and GSK3 associated with the axoneme in a phosphorylation-dependent manner. The level of active GSK3 correlated with flagellar length; early during flagellar regeneration, active GSK3 increased over basal levels. This increase in active GSK3 was rapidly lost within 30 min of regeneration as the level of active GSK3 decreased relative to the predeflagellation level. Taken together, these results suggest a possible role for GSK3 in regulating the assembly and length of flagella.
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PMID:Regulation of flagellar assembly by glycogen synthase kinase 3 in Chlamydomonas reinhardtii. 1547 Feb 59

The motility of cilia and flagella is powered by dynein ATPases associated with outer doublet microtubules. However, a flagellar kinesin-like protein that may function as a motor associates with the central pair complex. We determined that Chlamydomonas reinhardtii central pair kinesin Klp1 is a phosphoprotein and, like conventional kinesins, binds to microtubules in vitro in the presence of adenosine 5'-[beta,gamma-imido]triphosphate, but not ATP. To characterize the function of Klp1, we generated RNA interference expression constructs that reduce in vivo flagellar Klp1 levels. Klp1 knockdown cells have flagella that either beat very slowly or are paralyzed. EM image averages show disruption of two structures associated with the C2 central pair microtubule, C2b and C2c. Greatest density is lost from part of projection C2c, which is in a position to interact with doublet-associated radial spokes. Klp1 therefore retains properties of a motor protein and is essential for normal flagellar motility. We hypothesize that Klp1 acts as a conformational switch to signal spoke-dependent control of dynein activity.
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PMID:Regulation of flagellar dynein activity by a central pair kinesin. 1557 40

The Chlamydomonas anterograde intraflagellar transport motor, kinesin-2, is isolated as a heterotrimeric complex containing two motor subunits and a nonmotor subunit known as kinesin-associated polypeptide or KAP. One of the two motor subunits is encoded by the FLA10 gene. The sequence of the second motor subunit was obtained by mass spectrometry and sequencing. It shows 46.9% identity with the Fla10 motor subunit and the gene maps to linkage group XII/XIII near RPL9. The temperature-sensitive flagellar assembly mutants fla1 and fla8 are linked to this kinesin-2 motor subunit. In each strain, a unique single point mutation gives rise to a unique single amino acid substitution within the motor domain. The fla8 strain is named fla8-1 and the fla1 strain is named fla8-2. The fla8 and fla10 alleles show a chromosome loss phenotype. To analyze this chromosome loss phenotype, intragenic revertants of fla8-1, fla8-2, and fla10-14 were generated. The analysis of the mutants and the revertants demonstrates the importance of a pocket in the amino terminus of these motor subunits for both motor activity and for a novel, dominant effect on the fidelity of chromosome segregation.
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PMID:Mutant kinesin-2 motor subunits increase chromosome loss. 1594 18

Kinesin-like calmodulin-binding protein (KCBP), a member of the Kinesin-14 family, is a C-terminal microtubule motor with three unique domains including a myosin tail homology region 4 (MyTH4), a talin-like domain, and a calmodulin-binding domain (CBD). The MyTH4 and talin-like domains (found in some myosins) are not found in other reported kinesins. A calmodulin-binding kinesin called kinesin-C (SpKinC) isolated from sea urchin (Strongylocentrotus purpuratus) is the only reported kinesin with a CBD. Analysis of the completed genomes of Homo sapiens, Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and a red alga (Cyanidioschyzon merolae 10D) did not reveal the presence of a KCBP. This prompted us to look at the origin of KCBP and its relationship to SpKinC. To address this, we isolated KCBP from a gymnosperm, Picea abies, and a green alga, Stichococcus bacillaris. In addition, database searches resulted in identification of KCBP in another green alga, Chlamydomonas reinhardtii, and several flowering plants. Gene tree analysis revealed that the motor domain of KCBPs belongs to a clade within the Kinesin-14 (C-terminal motors) family. Only land plants and green algae have a kinesin with the MyTH4 and talin-like domains of KCBP. Further, our analysis indicates that KCBP is highly conserved in green algae and land plants. SpKinC from sea urchin, which has the motor domain similar to KCBP and contains a CBD, lacks the MyTH4 and talin-like regions. Our analysis indicates that the KCBPs, SpKinC, and a subset of the kinesin-like proteins are all more closely related to one another than they are to any other kinesins, but that either KCBP gained the MyTH4 and talin-like domains or SpKinC lost them.
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PMID:Origin and evolution of Kinesin-like calmodulin-binding protein. 1595 83

Chlamydomonas flagella contain a molecular chaperone now identified as HSP70A, a major cytoplasmic isoform. HSP70A synthesis is upregulated by deflagellation, and its distribution in the flagellum overlaps with the IFT kinesin-II motor FLA10. HSP70A may chaperone flagellar proteins during transport, participating in the assembly and maintenance of the flagellum.
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PMID:Characterization of a molecular chaperone present in the eukaryotic flagellum. 1615 Dec 52

Kinesin-like calmodulin-binding protein, KCBP, is a novel member of the C-kinesin superfamily first discovered in flowering plants. This minus-end-directed kinesin exhibits Ca(2+)-calmodulin-sensitive motor activity in vitro and has been implicated in trichome morphogenesis and cell division. A homologue of KCBP is also found in the unicellular, biflagellate green alga Chlamydomonas reinhardtii (CrKCBP). Unlike plant cells, Chlamydomonas cells do not form trichomes and do not assemble a phragmoplast before cell division. To test whether CrKCBP is involved in additional microtubule-based processes not observed in plants, we generated antibodies against the putative calmodulin-binding domain and used these antibodies in biochemical and localization studies. In interphase cells CrKCBP primarily localizes near the base of the flagella, although surprisingly, a small fraction also localizes along the length of the flagella. CrKCBP is bound to isolated axonemes in an ATP-dependent fashion and is not a component of the dynein arms, radial spokes or central apparatus. During mitosis, CrKCBP appears concentrated at the centrosomes during prophase and metaphase. However, during telophase and cytokinesis CrKCBP co-localizes with the microtubules associated with the phycoplast. These studies implicate CrKCBP in flagellar functions as well as cell division.
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PMID:A kinesin-like calmodulin-binding protein in Chlamydomonas: evidence for a role in cell division and flagellar functions. 1683 74

We present a new Chlamydomonas reinhardtii flagellar mutant in which central pair projections are missing and the central pair microtubules are twisted along the length of the flagellum. We have named this mutant tcp1 for twisted central pair. Immunoblots using an antibody that recognizes the heavy chain of sea urchin kinesin reveal that a 70 kDa protein present in wild-type and pf18 (central pairless) axonemes is absent in tcp1, suggesting the presence of an uncharacterized kinesin associated with the central pair apparatus. We demonstrate that the kinesin-like protein Klp1 is not attached to central pair microtubules in tcp1, but rather is located in, or is part of, a region we have termed the internal axonemal matrix. It is proposed that this matrix acts as a scaffold for axonemal proteins that may also be associated with the central pair apparatus.
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PMID:Ultrastructural and biochemical analysis of a new mutation in Chlamydomonas reinhardtii affecting the central pair apparatus. 1815

Cilia and flagella are dynamic organelles that are assembled and disassembled during cell differentiation, during stress, and during the cell cycle. Although intraflagellar transport (IFT) is well documented to be responsible for transport of ciliary/flagellar precursors from the cell body to the flagella, little is known about the molecular mechanisms for mobilizing the cell body-localized precursors to make them available for transport during organelle assembly or for disassembling the microtubule-based axoneme during shortening. Here, we show that Chlamydomonas kinesin-13 (CrKinesin-13), a member of the kinesin-13 family of microtubule depolymerizing kinesins best known for their roles in the cell cycle, functions in flagellar disassembly and flagellar assembly. Activation of a cell to generate new flagella induces rapid phosphorylation of CrKinesin-13, and activation of flagellar shortening induces the immediate transport of CrKinesin-13 via intraflagellar transport from the cell body into the flagella. Cells depleted of CrKinesin-13 by RNAi assemble flagella after cell division but are incapable of the rapid assembly of flagella that normally occurs after flagellar detachment. Furthermore, they are inhibited in flagellar shortening. Thus, CrKinesin-13 is dynamically regulated during flagellar assembly and disassembly in Chlamydomonas and functions in each.
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PMID:A microtubule depolymerizing kinesin functions during both flagellar disassembly and flagellar assembly in Chlamydomonas. 1926 63


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