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 kinesin superfamily of mechanochemical proteins has been implicated in a wide variety of cellular processes. We have begun studies of kinesins in the unicellular biflagellate alga, Chlamydomonas reinhardtii. A full-length cDNA, KLP1, has been cloned and sequenced, and found to encode a new member of the kinesin superfamily. An antibody was raised against the nonconserved tail region of the Klp1 protein, and it was used to probe for Klp1 in extracts of isolated flagella and in situ. Immunofluorescence of whole cells indicated that Klp1 was present in both the flagella and cell bodies. In wild-type flagella, Klp1 was found tightly to the axoneme; immunogold labeling of wild-type axonemal whole mounts showed that Klp1 was restricted to one of the two central pair microtubules at the core of the axoneme. Klp1 was absent from the flagella of mutants lacking the central pair microtubules, but was present in mutant flagella from pf16 cells, which contain an unstable C1 microtubule, indicating that Klp1 was bound to the C2 central pair microtubule. Localization of Klp1 to the C2 microtubule was confirmed by immunogold labeling of negatively stained and thin-sectioned axonemes. These findings suggest that Klp1 may play a role in rotation or twisting of the central pair microtubules.
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PMID:A new kinesin-like protein (Klp1) localized to a single microtubule of the Chlamydomonas flagellum. 820 60

Kinesin superfamily proteins (KIFs) are probable motors in vesicular and non-vesicular transport along microtubular tracks. Since a variety of KIFs have been recently identified in the motile flagella of Chlamydomonas, we sought to ascertain whether KIFs are also associated with the connecting cilia of vertebrate rod photoreceptors. As the only structural link between the rod inner segment and the photosensitive rod outer segment, the connecting cilium is thought to be the channel through which all material passes into and out of the outer segment from the rod cell body. We have performed immunological tests on isolated sunfish rod inner-outer segments (RIS-ROS) using two antibodies that recognize the conserved motor domain of numerous KIFs (anti-LAGSE, a peptide antibody, and anti-Klp1 head, generated against the N terminus of Chlamydomonas Klp1) as well as an antibody specific to a neuronal KIF, KIF3A. On immunoblots of RIS-ROS, LAGSE antibody detected a prominent band at approximately 117 kDa, which is likely to be kinesin heavy chain, and Klp1 head antibody detected a single band at approximately 170 kDa; KIF3A antibody detected a polypeptide at approximately 85 kDa which co-migrated with mammalian KIF3A and displayed ATP-dependent release from rod cytoskeletons. Immunofluorescence localizations with anti-LAGSE and anti-Klp1 head antibodies detected epitopes in the axoneme and ellipsoid, and immunoelectron microscopy with the LAGSE antibody showed that the connecting cilium region was particularly antigenic. Immunofluorescence with anti-KIF3A showed prominent labelling of the connecting cilium and the area surrounding its basal body; the outer segment axoneme and parts of the inner segment coincident with microtubules were also labelled. We propose that these putative kinesin superfamily proteins may be involved in the translocation of material between the rod inner and outer segments.
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PMID:Localization of kinesin superfamily proteins to the connecting cilium of fish photoreceptors. 871 80

In order to generate the complex waveforms typical of beating cilia and flagella, the action of the dynein arms must be regulated. This regulation not only depends on the presence of multiple dynein isoforms, but also clearly involves other structures in the axoneme such as the radial spokes and central apparatus; mutants lacking these structures have paralyzed flagella. In this article, we review recent progress in identifying protein components of the central apparatus and discuss the role of these components in regulation of flagellar motility and central apparatus assembly. The central apparatus is composed of two single microtubules and their associated structures which include the central pair projections, the central pair bridges linking the two tubules, and the central pair caps which are attached to the distal or plus ends of the microtubules. To date, the genes encoding four components of the central apparatus have been cloned, PF15, PF16, PF20 and KLP1. PF16, PF20 and KLP1 have been sequenced and their gene products localized. Two additional components have been identified immunologically, a 110 kD polypeptide recognized by an antibody generated against highly conserved kinesin peptide sequence, and a 97 kD polypeptide recognized by CREST antisera. Based on a variety of data, one model that has emerged to explain the role of the central apparatus in flagellar motility is that the central apparatus ultimately regulates dynein through interactions with the radial spokes. The challenge now is to determine the precise mechanism by which the polypeptides comprising the central apparatus and the radial spokes interact to transduce a regulatory signal to the dynein arms. In terms of assembly, the central apparatus microtubules assemble with their plus ends distal to the cell body but, unlike the nine doublet microtubules, they are not nucleated from the basal bodies. Since some central apparatus defective mutants fail to assemble the entire central apparatus, their gene products may eventually prove to have microtubule nucleating or stabilizing properties. By continuing to identify the genes that encode central apparatus components, we will begin to understand the contribution of these microtubules to flagellar motility and gain insight into their nucleation, assembly, and stability.
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PMID:The role of central apparatus components in flagellar motility and microtubule assembly. 929 36

To understand the functions of microtubule motors in vertebrate development, we are investigating the kinesin-like proteins (KLPs) of the zebrafish, Danio rerio. Here we describe the structure, intracellular distribution, and function of zebrafish mitotic KLP1 (Mklp1). The zebrafish mklp1 gene that encodes this 867-amino acid protein maps to a region of zebrafish linkage group 18 that is syntenic with part of human chromosome 15. In zebrafish AB9 fibroblasts and in COS-7 cells, the zebrafish Mklp1 protein decorates spindle microtubules at metaphase, redistributes to the spindle midzone during anaphase, and becomes concentrated in the midbody during telophase and cytokinesis. The motor is detected consistently in interphase nuclei of COS cells and occasionally in those of AB9 cells. Nuclear targeting of Mklp1 is conferred by two basic motifs located in the COOH terminus of the motor. In cleaving zebrafish embryos, green fluorescent protein (GFP)-tagged Mklp1 is found in the nucleus in interphase and associates with microtubules of the spindle midbody in cytokinesis. One- or two-cell embryos injected with synthetic mRNAs encoding dominant-negative variants of GFP-Mklp1 frequently fail to complete cytokinesis during cleavage, resulting in formation of multinucleated blastomeres. Our results indicate that the zebrafish Mklp1 motor performs a critical function that is required for completion of embryonic cytokinesis.
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PMID:Zebrafish mitotic kinesin-like protein 1 (Mklp1) functions in embryonic cytokinesis. 1184 31

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

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

Numerous eukaryote genome projects have uncovered a variety of kinesins of unknown function. The kinesin 9 family is limited to flagellated species. Our phylogenetic experiments revealed two subfamilies: KIF9A (including Chlamydomonas reinhardtii KLP1) and KIF9B (including human KIF6). The function of KIF9A and KIF9B was investigated in the protist Trypanosoma brucei that possesses a single motile flagellum. KIF9A and KIF9B are strongly associated with the cytoskeleton and are required for motility. KIF9A is localized exclusively in the axoneme, and its depletion leads to altered motility without visible structural modifications. KIF9B is found in both the axoneme and the basal body, and is essential for the assembly of the paraflagellar rod (PFR), a large extra-axonemal structure. In the absence of KIF9B, cells grow abnormal flagella with excessively large blocks of PFR-like material that alternate with regions where only the axoneme is present. The functional diversity of the kinesin 9 family illustrates the capacity for adaptation of organisms to suit specific cytoskeletal requirements.
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PMID:Kinesin 9 family members perform separate functions in the trypanosome flagellum. 1994 86