scholarly journals The Neurospora organelle motor: a distant relative of conventional kinesin with unconventional properties.

1995 ◽  
Vol 6 (11) ◽  
pp. 1605-1618 ◽  
Author(s):  
G Steinberg ◽  
M Schliwa
Keyword(s):  
Molecular Motors ◽  
High Rate ◽  
Organelle Transport ◽  
Sequence Organization ◽  
C Terminus ◽  
Microtubule Transport ◽  
Molecular Phylogenetic ◽  
Functional Features ◽  
Conventional Kinesin ◽  
Distant Relative

The "conventional" kinesins comprise a conserved family of molecular motors for organelle transport that have been identified in various animal species. Organelle motors from other phyla have not yet been analyzed at the molecular level. Here we report the identification, biochemical and immunological characterization, and molecular cloning of a cytoplasmic motor in a "lower" eukaryote, the Ascomycete fungus Neurospora crassa. This motor, termed Nkin (for Neurospora kinesin), exhibits several unique structural and functional features, including a high rate of microtubule transport, a lack of copurifying light chains, a second P-loop motif, and an overall sequence organization reminiscent of a kinesin-like protein. However, a greater than average sequence homology in the motor domain and the presence of a highly conserved region in the C-terminus identify Nkin as a distant relative of the family of conventional kinesins. A molecular phylogenetic analysis suggests Nkin to have diverged early in the evolution of this family of motors. The discovery of Nkin may help identify domains important for specific biological functions in conventional kinesins.

scholarly journals Peroxisomes move by hitchhiking on early endosomes using the novel linker protein PxdA

2015 ◽  
Author(s):  
John Salogiannis ◽  
Martin J. Egan ◽  
Samara L. Reck-Peterson
Keyword(s):  
Molecular Motors ◽  
Intracellular Transport ◽  
Coiled Coil ◽  
Leading Edge ◽  
Time Lapse ◽  
Early Endosome ◽  
Organelle Transport ◽  
The Novel ◽  
Coiled Coil Region ◽  
Early Endosomes

Eukaryotic cells use microtubule-based intracellular transport for the delivery of many subcellular cargos, including organelles. The canonical view of organelle transport is that organelles directly recruit molecular motors via cargo-specific adaptors. In contrast to this view, we show here that peroxisomes move by hitchhiking on early endosomes, an organelle that directly recruits the transport machinery. Using the filamentous fungus Aspergillus nidulans we find that hitchhiking is mediated by a novel endosome-associated linker protein, PxdA. PxdA is required for normal distribution and long-range movement of peroxisomes, but not early endosomes or nuclei. Using simultaneous time-lapse imaging we find that early endosome-associated PxdA localizes to the leading edge of moving peroxisomes. We identify a coiled-coil region within PxdA that is necessary and sufficient for early endosome localization and peroxisome distribution and motility. These results present a new mechanism of microtubule-based organelle transport where peroxisomes hitchhike on early endosomes and identify PxdA as the novel linker protein required for this coupling.

scholarly journals What is a Wood-Warbler? Molecular Characterization of a Monophyletic Parulidae

The Auk ◽  
2002 ◽  
Vol 119 (3) ◽  
pp. 695-714 ◽  
Author(s):  
I. J. Lovette ◽  
E. Bermingham
Keyword(s):  
Dna Sequences ◽  
Nuclear Dna ◽  
Morphological Characters ◽  
High Rate ◽  
Nucleotide Substitutions ◽  
Wood Warbler ◽  
Wood Warblers ◽  
Phylogenetic Level ◽  
Molecular Phylogenetic

AbstractThe wood-warblers (family Parulidae) fall within a radiation of passerine birds commonly known as the New World nine-primaried oscines. Defining familial relationships within that radiation has previously been challenging because of its extremely high diversity, a paucity of phylogenetically informative morphological characters, and an apparent high rate of cladogenesis early in the radiation's history. Here, analyses of mitochondrial and nuclear DNA sequences demonstrate that the 25 extant genera traditionally placed in the Parulidae do not form a monophyletic group. Instead, all reconstructions identify a well-resolved clade of 19 genera (Vermivora, Parula, Dendroica, Catharopeza, Mniotilta, Setophaga, Protonotaria, Helmitheros, Limnothlypis, Seiurus, Oporornis, Geothlypis, Wilsonia, Cardellina, Ergaticus, Myioborus, Euthlypis, Basileuterus, and Phaeothlypis) that are all morphologically typical wood-warblers traditionally placed in the Parulidae. Six genera traditionally assigned to the Parulidae—Microligea, Teretistris, Zeledonia, Icteria, Granatellus, and Xenoligea—fall outside this highly supported clade in all mtDNA-based and nuclear DNA-based reconstructions, and each is probably more closely allied to taxa traditionally placed in other nine-primaried oscine families. The long, well-supported, and independently confirmed internode at the base of this wood-warbler clade provides the opportunity to define a monophyletic Parulidae using several complementary molecular phylogenetic criteria. Support for those relationships comes from reconstructions based on a range of nucleotide-intensive (from 894 to 3,638 nucleotides per taxon) and taxon-intensive (45 to 128 species) analyses of mtDNA sequences, as well as independent reconstructions based on nucleotide substitutions in the nuclear-encoded c-mos gene. Furthermore, the 19 typical wood-warbler genera share a synapomorphic one-codon c-mos deletion not found in other passerines. At a slightly deeper phylogenetic level, our mtDNA-based reconstructions are consistent with previous morphologic and genetic studies in suggesting that many nine-primaried oscine taxa have unanticipated affinities, that many lineages arose during an early and explosive period of cladogenesis, and that the generation of a robust nine-primaried oscine phylogeny will require robust taxonomic sampling and extensive phylogenetic information.

scholarly journals Cytoplasmic Dynein, the Dynactin Complex, and Kinesin Are Interdependent and Essential for Fast Axonal Transport

1999 ◽  
Vol 10 (11) ◽  
pp. 3717-3728 ◽  
Author(s):  
MaryAnn Martin ◽  
Stanley J. Iyadurai ◽  
Andrew Gassman ◽  
Joseph G. Gindhart ◽  
Thomas S. Hays ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Heavy Chain ◽  
Cytoplasmic Dynein ◽  
Genetic Interactions ◽  
Organelle Transport ◽  
Fast Axonal Transport ◽  
Anterograde Transport ◽  
Dynein Heavy Chain ◽  
Conventional Kinesin ◽  
Dynactin Complex

In axons, organelles move away from (anterograde) and toward (retrograde) the cell body along microtubules. Previous studies have provided compelling evidence that conventional kinesin is a major motor for anterograde fast axonal transport. It is reasonable to expect that cytoplasmic dynein is a fast retrograde motor, but relatively few tests of dynein function have been reported with neurons of intact organisms. In extruded axoplasm, antibody disruption of kinesin or the dynactin complex (a dynein activator) inhibits both retrograde and anterograde transport. We have tested the functions of the cytoplasmic dynein heavy chain (cDhc64C) and the p150Glued(Glued) component of the dynactin complex with the use of genetic techniques in Drosophila.cDhc64C and Glued mutations disrupt fast organelle transport in both directions. The mutant phenotypes, larval posterior paralysis and axonal swellings filled with retrograde and anterograde cargoes, were similar to those caused by kinesin mutations. Why do specific disruptions of unidirectional motor systems cause bidirectional defects? Direct protein interactions of kinesin with dynein heavy chain and p150Glued were not detected. However, strong dominant genetic interactions between kinesin, dynein, and dynactin complex mutations in axonal transport were observed. The genetic interactions between kinesin and either Glued orcDhc64C mutations were stronger than those betweenGlued and cDhc64C mutations themselves. The shared bidirectional disruption phenotypes and the dominant genetic interactions demonstrate that cytoplasmic dynein, the dynactin complex, and conventional kinesin are interdependent in fast axonal transport.

scholarly journals Conventional Kinesin Mediates Microtubule-Microtubule Interactions In Vivo

2006 ◽  
Vol 17 (2) ◽  
pp. 907-916 ◽  
Author(s):  
Anne Straube ◽  
Gerd Hause ◽  
Gero Fink ◽  
Gero Steinberg
Keyword(s):  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Binding Activity ◽  
C Terminus ◽  
Cross Bridges ◽  
Conventional Kinesin ◽  
Motor Head

Conventional kinesin is a ubiquitous organelle transporter that moves cargo toward the plus-ends of microtubules. In addition, several in vitro studies indicated a role of conventional kinesin in cross-bridging and sliding microtubules, but in vivo evidence for such a role is missing. In this study, we show that conventional kinesin mediates microtubule-microtubule interactions in the model fungus Ustilago maydis. Live cell imaging and ultrastructural analysis of various mutants in Kin1 revealed that this kinesin-1 motor is required for efficient microtubule bundling and participates in microtubule bending in vivo. High levels of Kin1 led to increased microtubule bending, whereas a rigor-mutation in the motor head suppressed all microtubule motility and promoted strong microtubule bundling, indicating that kinesin can form cross-bridges between microtubules in living cells. This effect required a conserved region in the C terminus of Kin1, which was shown to bind microtubules in vitro. In addition, a fusion protein of yellow fluorescent protein and the Kin1tail localized to microtubule bundles, further supporting the idea that a conserved microtubule binding activity in the tail of conventional kinesins mediates microtubule-microtubule interactions in vivo.

scholarly journals Essential Domains for Ribonucleoprotein Complex Formation Required for Retrotransposition of Telomere-Specific Non-Long Terminal Repeat Retrotransposon SART1

2006 ◽  
Vol 26 (13) ◽  
pp. 5168-5179 ◽  
Author(s):  
Takumi Matsumoto ◽  
Mitsuhiro Hamada ◽  
Mizuko Osanai ◽  
Haruhiko Fujiwara
Keyword(s):  
Long Terminal Repeat ◽  
Expression System ◽  
Baculovirus Expression System ◽  
Open Reading Frames ◽  
Terminal Repeat ◽  
Ltr Retrotransposons ◽  
C Terminus ◽  
Functional Features

ABSTRACT Non-long terminal repeat (LTR) retrotransposons are major components of the higher eukaryotic genome. Most of them have two open reading frames (ORFs): ORF2 encodes mainly the endonuclease and reverse transcriptase domains, but the functional features of ORF1 remain largely unknown. We used telomere-specific non-LTR retrotransposon SART1 in Bombyx mori and clarified essential roles of the ORF1 protein (ORF1p) in ribonucleoprotein (RNP) formation by novel approaches: in vitro reconstitution and in vivo/in vitro retrotransposition assays using the baculovirus expression system. Detailed mutation analyses showed that each of the three CCHC motifs at the ORF1 C terminus are essential for SART1 retrotransposition and are involved in packaging the SART1 mRNA specifically into RNP. We also demonstrated that amino acid residues 555 to 567 and 285 to 567 in the SART1 ORF1p are crucial for the ORF1p-ORF1p and ORF1p-ORF2p interactions, respectively. The loss of these domains abolishes protein-protein interaction, leading to SART1 retrotransposition deficiency. These data suggest that systematic formation of RNP composed of ORF1p, ORF2p, and mRNA is mainly mediated by ORF1p domains and is a common, essential step for many non-LTR retrotransposons encoding the two ORFs.

scholarly journals Common general anesthetic propofol impairs kinesin processivity

2017 ◽  
Vol 114 (21) ◽  
pp. E4281-E4287 ◽  
Author(s):  
Brandon M. Bensel ◽  
Stephanie Guzik-Lendrum ◽  
Erin M. Masucci ◽  
Kellie A. Woll ◽  
Roderic G. Eckenhoff ◽  
...  
Keyword(s):  
Single Molecule ◽  
Molecular Motors ◽  
Intraflagellar Transport ◽  
General Anesthetic ◽  
Allosteric Site ◽  
Allosteric Sites ◽  
Additional Protein ◽  
Velocity Effect ◽  
Processive Stepping ◽  
Conventional Kinesin

Propofol is the most widely used i.v. general anesthetic to induce and maintain anesthesia. It is now recognized that this small molecule influences ligand-gated channels, including the GABAA receptor and others. Specific propofol binding sites have been mapped using photoaffinity ligands and mutagenesis; however, their precise target interaction profiles fail to provide complete mechanistic underpinnings for the anesthetic state. These results suggest that propofol and other common anesthetics, such as etomidate and ketamine, may target additional protein networks of the CNS to contribute to the desired and undesired anesthesia end points. Some evidence for anesthetic interactions with the cytoskeleton exists, but the molecular motors have received no attention as anesthetic targets. We have recently discovered that propofol inhibits conventional kinesin-1 KIF5B and kinesin-2 KIF3AB and KIF3AC, causing a significant reduction in the distances that these processive kinesins can travel. These microtubule-based motors are highly expressed in the CNS and the major anterograde transporters of cargos, such as mitochondria, synaptic vesicle precursors, neurotransmitter receptors, cell signaling and adhesion molecules, and ciliary intraflagellar transport particles. The single-molecule results presented show that the kinesin processive stepping distance decreases 40–60% with EC50 values <100 nM propofol without an effect on velocity. The lack of a velocity effect suggests that propofol is not binding at the ATP site or allosteric sites that modulate microtubule-activated ATP turnover. Rather, we propose that a transient propofol allosteric site forms when the motor head binds to the microtubule during stepping.

scholarly journals Protective Role of Carbonic Anhydrases III and VII in Cellular Defense Mechanisms upon Redox Unbalance

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Anna Di Fiore ◽  
Daria M. Monti ◽  
Andrea Scaloni ◽  
Giuseppina De Simone ◽  
Simona M. Monti
Keyword(s):  
Oxidative Stress ◽  
Oxidative Damage ◽  
Antioxidant Properties ◽  
Stress Conditions ◽  
Sulfhydryl Groups ◽  
High Rate ◽  
Molecular Surface ◽  
Carbonic Anhydrases ◽  
Cellular Defense ◽  
Functional Features

Under oxidative stress conditions, several constitutive cellular defense systems are activated, which involve both enzymatic systems and molecules with antioxidant properties such as glutathione and vitamins. In addition, proteins containing reactive sulfhydryl groups may eventually undergo reversible redox modifications whose products act as protective shields able to avoid further permanent molecular oxidative damage either in stressful conditions or under pathological circumstances. After the recovery of normal redox conditions, the reduced state of protein sulfhydryl groups is restored. In this context, carbonic anhydrases (CAs) III and VII, which are human metalloenzymes catalyzing the reversible hydration of carbon dioxide to bicarbonate and proton, have been identified to play an antioxidant role in cells where oxidative damage occurs. Both proteins are mainly localized in tissues characterized by a high rate of oxygen consumption, and contain on their molecular surface two reactive cysteine residues eventually undergoing S-glutathionylation. Here, we will provide an overview on the molecular and functional features of these proteins highlighting their implications into molecular processes occurring during oxidative stress conditions.

scholarly journals Fission Yeast F-box Protein Pof3 Is Required for Genome Integrity and Telomere Function

2002 ◽  
Vol 13 (1) ◽  
pp. 211-224 ◽  
Author(s):  
Satoshi Katayama ◽  
Kenji Kitamura ◽  
Anna Lehmann ◽  
Osamu Nikaido ◽  
Takashi Toda
Keyword(s):  
Cell Cycle ◽  
Fission Yeast ◽  
Ubiquitin Ligase ◽  
Repeat Motif ◽  
High Rate ◽  
Genome Integrity ◽  
Gene Encoding ◽  
Cell Cycle Delay ◽  
C Terminus ◽  
F Box Protein

The Skp1-Cullin-1/Cdc53-F-box protein (SCF) ubiquitin ligase plays an important role in various biological processes. In this enzyme complex, a variety of F-box proteins act as receptors that recruit substrates. We have identified a fission yeast gene encoding a novel F-box protein Pof3, which contains, in addition to the F-box, a tetratricopeptide repeat motif in its N terminus and a leucine-rich-repeat motif in the C terminus, two ubiquitous protein–protein interaction domains. Pof3 forms a complex with Skp1 and Pcu1 (fission yeast cullin-1), suggesting that Pof3 functions as an adaptor for specific substrates. In the absence of Pof3, cells exhibit a number of phenotypes reminiscent of genome integrity defects. These include G2 cell cycle delay, hypersensitivity to UV, appearance of lagging chromosomes, and a high rate of chromosome loss.pof3 deletion strains are viable because the DNA damage checkpoint is continuously activated in the mutant, and this leads to G2 cell cycle delay, thereby preventing the mutant from committing lethal mitosis. Pof3 localizes to the nucleus during the cell cycle. Molecular analysis reveals that in this mutant the telomere is substantially shortened and furthermore transcriptional silencing at the telomere is alleviated. The results highlight a role of the SCFPof3 ubiquitin ligase in genome integrity via maintaining chromatin structures.

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