DOCSLIB.ORG

Flagella Apparatus

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Flagella Apparatus MOTILE CELL Characters and Character States Location code / cell type ZO, zoospore Flagella apparatus Kinetosome Electron-opaque material in core in kinetosome 0, absent (everything else); 1, present (Kappamyces). Electron-opaque material in axoneme core and between axoneme and flagellar membrane 0, absent; 1, present (many Chytridiales). Kinetosome characters Scalloped ring within kinetosome, extensions of the A, B, or C microtubule Flagellum coating 0, absent; 1, present (Polyphagus euglenae). Number of flagella 0, one 1, multiple Kinetosome-associated structures (KAS) Kinetosome support 0, absent 1, kinetosome props; 2, broken kinetosome props (Olpidium radicale); 3, saddle-like structure surrounding kinetosome (Neocallimastigales) Kinetosome-associated plates 0, absent; 1, present. Kinetosome-associated spur 0, absent; 1, present. Kinetosome-associated shield 0, absent; 1, present. Kinetosome-associated veil 0, absent; 1, present. Anteriorly oriented kinetosome microtubule organizing center (MTOC) (Spizellomycetales) 0, absent; 1, simple solid, not laminate, only one part (Spizellomyces); 2, stacked plates with radiating anteriorly oriented microtubules (Powellomyces) 3, stacked plates with laterally anteriorly oriented microtubules (Gaerteromyces) 4, compound, two in stacked arrangement (Kochiomyces) 5, tripartitalcar rod with 3 lobes in cross-section Primary microtubule roots 0, absent; 1, 2-5 parallel microtubules are stacked with space between them, no connectors (Rhyzophydium); 2, approx. 6-7 parallel microtubules chord-like; 3, more than 20 parallel microtubules, bundled and have connectors/linkers between them (Nowakowskiella); 4, microtubules posterior to anterior, parallel to kinetosome triplets (Batracomyces – not separated like Rhysophydium). Striated rhizoplast 0, absent; 1, present. Flagellar rootlet absolute configuration 0, absent; 1, 20 degrees left; 2, 10 degrees right; 3, 50 degrees left. Flagella rootlets 0, absent; 1, of 2-16 microtubules connecting kinetosome to rumposome (Chytridiales); 2, of 27 microtubules in groups of 3 extending from anterior of kinetosome (Blastocladiales); 3, root of two parts: a striated disk extending part way around kinetosome, and microtubules extending anteriorly from kinetosome; (Monoblepharidales); 4, extending anteriorly without regular arrangement from spur on kinetosome; 5, microtubules in cone arising from MTOC anterior end of kinetosome. Spatial dimension of flagellar rootlet microtubules 0, absent; 1, diverging; 2, longitudinally stacked in single file; 3, layered and cross-linked; 4, layered and not cross-linked; 5, layered and embedded in electron-opaque material. Non-flagellated centriole Non-flagellated centriole (NFC) 0, absent; 1, parallel to kinetosome; 2, oblique to kinetosome; 3, at right angle to kinetosome. Length of non-flagellated centriole (NFC) compared to centriole (* caveat) 0, short (Monoblepharidales, Kappamyces); 1, equal; 2, long (Lacustromyces). Kinetosome-NFC bridge 0, absent; 1, fibers transverse; 2, fibers parallel; 3, homogeneous anterior. NFC-associated veil 0, absent; 1, present. Other cell features Paracrystalline body 0, absent; 1, present (Blastocladiales, Chytridiomyces clade and Phlyctochytrium). Ribosome organization 0, scattered ribosomes; 1, core area of compacted ribosomes partially or completely enclosed by endoplasmic reticulum; 2, in nuclear cap; 3, loosely enclosed by endoplasmic reticulum and surrounding nucleus; 4, in aggregates at anterior of cell. Mitochondria 0, absent (hydrogenosomes); 1, single; 2, multiple. Cisterna 0, absent; 1, simple; 2, fenestrated (rumposome). Annular cisterna 0, absent; 1, present (Monoblepharidales). Paraxonemal rod 0, absent; 1, present. Water expulsion vacuole 0, absent; (Chytridiales); 1, present (Spizellomycetales, Monoblepharidales). Golgi apparatus 0, stacked cisternae; 1, absence of stacked cisternae. Location of Golgi apparatus 0, absent; 1, associated with flagellar rootlet; 3, not associated with flagellar rootlet. Relationship of microbodies to lipid(s) [pending] 0, on lipid; 1, MB with single lipids; 2, MB with multiple lipids; Dissect along ordinal lines. Location of cisterna to lipid(s) [pending] Dissect along ordinal lines. 0, Adjacent to lipids (Chytridiales); 1, Backs microbody (Blastocladiales); 2, Fenestrated cisternae (rumposome) backed by microbody (Monoblepharidales); 3, absent (Batracochytrium, Locustromyces). Location of mitochondria to lipid(s) [pending] proximal to microbodies, keep unresolved; dissect along ordinal lines. Nuclear spur 0, absent; 1, present. Nuclear location 0, distal to kinteosome; 1, proximal to kinetosome; 2, connected to kinetosome. Posterior dome composed of peripheral granules and array of megatubules 0, absent; 1, present. .
Load more

Recommended publications
  • 3 Saccharomyces Cell Structure
    Genetic Techniques for Biological Research Corinne A. Michels Copyright q 2002 John Wiley & Sons, Ltd ISBNs: 0-471-89921-6 (Hardback); 0-470-84662-3 (Electronic) 3 Saccharomyces Cell Structure Saccharomycescerevisiue is aeukaryote and as such containsthe subcellular organelles commonlyfound in eukaryotes.The structure and function of these organelles is fundamentally the same as it is in other eukaryotes with less versatile systems for genetic analysis, and for this reason Saccharomyces is the organism of choice for many cell biologists. For a truly in-depth review of Saccharomyces cell structure and function, the reader is referred to The Molecular and Cellular Biology of theYeast Saccharomyces: Vol. 3: CellCycle and Cell Biology (Broach etal., 1997). The discussion here will provide a very brief overview of the cell structure and will focus on certain unique features of Saccharomyces cell structure in order to facilitate reading of the literature. CELL SHAPE AND GROWTH PATTERNS Underusual culture conditions, Saccharomyces is ellipsoidaUovoid in shapeand approximately 5-10 pm long by 3-7 pm wide. This is referred to as the yeast form. Figure 3.1 shows a scanning electron micrograph (SEM) of a cell in the yeast form. Cell division is by budding; that is, a smaller ovoid daughter cell formsas a projection from the surface of the mother cell. Haploid cells are generally about one-half the volume of diploid cells. The characteristic shape is maintained by a rigid cell wall that completely surrounds the plasma membrane of Saccharomyces. Changes in this shape involve remodeling of the cell wall and occur during budding, mating,and pseudohyphal differentiation.
    [Show full text]
  • The Cytoskeleton of Giardia Lamblia
    International Journal for Parasitology 33 (2003) 3–28 www.parasitology-online.com Invited review The cytoskeleton of Giardia lamblia Heidi G. Elmendorfa,*, Scott C. Dawsonb, J. Michael McCafferyc aDepartment of Biology, Georgetown University, 348 Reiss Building 37th and O Sts. NW, Washington, DC 20057, USA bDepartment of Molecular and Cell Biology, University of California Berkeley, 345 LSA Building, Berkeley, CA 94720, USA cDepartment of Biology, Johns Hopkins University, Integrated Imaging Center, Baltimore, MD 21218, USA Received 18 July 2002; received in revised form 18 September 2002; accepted 19 September 2002 Abstract Giardia lamblia is a ubiquitous intestinal pathogen of mammals. Evolutionary studies have also defined it as a member of one of the earliest diverging eukaryotic lineages that we are able to cultivate and study in the laboratory. Despite early recognition of its striking structure resembling a half pear endowed with eight flagella and a unique ventral disk, a molecular understanding of the cytoskeleton of Giardia has been slow to emerge. Perhaps most importantly, although the association of Giardia with diarrhoeal disease has been known for several hundred years, little is known of the mechanism by which Giardia exacts such a toll on its host. What is clear, however, is that the flagella and disk are essential for parasite motility and attachment to host intestinal epithelial cells. Because peristaltic flow expels intestinal contents, attachment is necessary for parasites to remain in the small intestine and cause diarrhoea, underscoring the essential role of the cytoskeleton in virulence. This review presents current day knowledge of the cytoskeleton, focusing on its role in motility and attachment.
    [Show full text]
  • The Ultrastructure of Spermatozoa and Spermiogenesis in Pyramidellid Gastropods, and Its Systematic Importance John M
    HELGOLANDER MEERESUNTERSUCHUNGEN Helgol~inder Meeresunters. 42,303-318 (1988) The ultrastructure of spermatozoa and spermiogenesis in pyramidellid gastropods, and its systematic importance John M. Healy School of Biological Sciences (Zoology, A08), University of Sydney; 2006, New South Wales, Australia ABSTRACT: Ultrastructural observations on spermiogenesis and spermatozoa of selected pyramidellid gastropods (species of Turbonilla, ~gulina, Cingufina and Hinemoa) are presented. During spermatid development, the condensing nucleus becomes initially anterio-posteriorly com- pressed or sometimes cup-shaped. Concurrently, the acrosomal complex attaches to an electron- dense layer at the presumptive anterior pole of the nucleus, while at the opposite (posterior) pole of the nucleus a shallow invagination is formed to accommodate the centriolar derivative. Midpiece formation begins soon after these events have taken place, and involves the following processes: (1) the wrapping of individual mitochondria around the axoneme/coarse fibre complex; (2) later internal metamorphosis resulting in replacement of cristae by paracrystalline layers which envelope the matrix material; and (3) formation of a glycogen-filled helix within the mitochondrial derivative (via a secondary wrapping of mitochondria). Advanced stages of nuclear condensation {elongation, transformation of fibres into lamellae, subsequent compaction) and midpiece formation proceed within a microtubular sheath ('manchette'). Pyramidellid spermatozoa consist of an acrosomal complex (round
    [Show full text]
  • Cytoskeleton Cytoskeleton
    CYTOSKELETON CYTOSKELETON The cytoskeleton is composed of three principal types of protein filaments: actin filaments, intermediate filaments, and microtubules, which are held together and linked to subcellular organelles and the plasma membrane by a variety of accessory proteins Muscle Contraction • Skeletal muscles are bundles of muscle fibers • Most of the cytoplasm consists of myofibrils, which are cylindrical bundles of two types of filaments: thick filaments of myosin (about 15 run in diameter) and thin filaments of actin (about 7 nm in diameter). • Each myofibril is organized as a chain of contractile units called sarcomeres, which are responsible for the striated appearance of skeletal and cardiac muscle. Structure of muscle cells Sarcomere • The ends of each sarcomere are defined by the Z disc. • Within each sarcomere, dark bands (called A bands because they are anisotropic when viewed with polarized light) alternate with light bands (called I bands for isotropic). • The I bands contain only thin (actin) filaments, whereas the A bands contain thick (myosin) filaments. • The myosin and actin filaments overlap in peripheral regions of the A band, whereas a middle region (called the H zone) contains only myosin. Muscle contraction • The basis for understanding muscle contraction is the sliding filament model, first proposed in 1954 both by Andrew Huxley and Ralph Niedergerke and by Hugh Huxley and Jean Hanson • During muscle contraction each sarcomere shortens, bringing the Z discs closer together. • There is no change in the width of the A band, but both the I bands and the H zone almost completely disappear. • These changes are explained by the actin and myosin filaments sliding past one another so that the actin filaments move into the A band and H zone.
    [Show full text]
  • Cilia and Flagella: from Discovery to Disease Dylan J
    Dartmouth Undergraduate Journal of Science Volume 20 Article 2 Number 1 Assembly 2017 Cilia and Flagella: From Discovery to Disease Dylan J. Cahill Dylan Cahill, [email protected] Follow this and additional works at: https://digitalcommons.dartmouth.edu/dujs Part of the Engineering Commons, Life Sciences Commons, Medicine and Health Sciences Commons, Physical Sciences and Mathematics Commons, and the Social and Behavioral Sciences Commons Recommended Citation Cahill, Dylan J. (2017) "Cilia and Flagella: From Discovery to Disease," Dartmouth Undergraduate Journal of Science: Vol. 20 : No. 1 , Article 2. Available at: https://digitalcommons.dartmouth.edu/dujs/vol20/iss1/2 This Research Article is brought to you for free and open access by the Student-led Journals and Magazines at Dartmouth Digital Commons. It has been accepted for inclusion in Dartmouth Undergraduate Journal of Science by an authorized editor of Dartmouth Digital Commons. For more information, please contact [email protected]. BIOLOGY Cilia and Flagella: FromCilia and Discovery Flagella: to Disease From Discovery to Disease BY DYLAN CAHILL ‘18 Introduction certain insect sperm fagella (3, 5, 6). A unique Figure 1: Chlamydomonas intracellular transport mechanism known as reinhardtii, a single-celled, bi- In 1674, peering through the lens of a crude flagellate green alga, viewed intrafagellar transport is responsible for the light microscope, Antoni van Leeuwenhoek with a scanning electron assembly and maintenance of these organelles Chlamydomonas observed individual living cells for the frst time microscope. is (3, 6). Cilia and fagella are primarily composed a model organism in flagellar in history (1). He noted long, thin appendages of the protein tubulin, which polymerizes into dynamics and motility studies.
    [Show full text]
  • Ciliary Dyneins and Dynein Related Ciliopathies
    cells Review Ciliary Dyneins and Dynein Related Ciliopathies Dinu Antony 1,2,3, Han G. Brunner 2,3 and Miriam Schmidts 1,2,3,* 1 Center for Pediatrics and Adolescent Medicine, University Hospital Freiburg, Freiburg University Faculty of Medicine, Mathildenstrasse 1, 79106 Freiburg, Germany; [email protected] 2 Genome Research Division, Human Genetics Department, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 KL Nijmegen, The Netherlands; [email protected] 3 Radboud Institute for Molecular Life Sciences (RIMLS), Geert Grooteplein Zuid 10, 6525 KL Nijmegen, The Netherlands * Correspondence: [email protected]; Tel.: +49-761-44391; Fax: +49-761-44710 Abstract: Although ubiquitously present, the relevance of cilia for vertebrate development and health has long been underrated. However, the aberration or dysfunction of ciliary structures or components results in a large heterogeneous group of disorders in mammals, termed ciliopathies. The majority of human ciliopathy cases are caused by malfunction of the ciliary dynein motor activity, powering retrograde intraflagellar transport (enabled by the cytoplasmic dynein-2 complex) or axonemal movement (axonemal dynein complexes). Despite a partially shared evolutionary developmental path and shared ciliary localization, the cytoplasmic dynein-2 and axonemal dynein functions are markedly different: while cytoplasmic dynein-2 complex dysfunction results in an ultra-rare syndromal skeleto-renal phenotype with a high lethality, axonemal dynein dysfunction is associated with a motile cilia dysfunction disorder, primary ciliary dyskinesia (PCD) or Kartagener syndrome, causing recurrent airway infection, degenerative lung disease, laterality defects, and infertility. In this review, we provide an overview of ciliary dynein complex compositions, their functions, clinical disease hallmarks of ciliary dynein disorders, presumed underlying pathomechanisms, and novel Citation: Antony, D.; Brunner, H.G.; developments in the field.
    [Show full text]
  • 3D Structure of Eukaryotic Flagella in a Quiescent State Revealed by Cryo-Electron Tomography
    3D structure of eukaryotic flagella in a quiescent state revealed by cryo-electron tomography Daniela Nicastro*†, J. Richard McIntosh‡§, and Wolfgang Baumeister* *Abteilung Molekulare Strukturbiologie, Max-Planck-Institut fu¨r Biochemie, 82152 Martinsried, Germany; and ‡Laboratory for 3D Electron Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, UCB 347, University of Colorado, Boulder, CO 80309 Contributed by J. Richard McIntosh, September 21, 2005 We have used cryo-electron tomography to investigate the 3D position. McEwen et al. (12) have used electron tomography structure and macromolecular organization of intact, frozen- (ET) to study chemically fixed and resin-embedded cilia from hydrated sea urchin sperm flagella in a quiescent state. The newt lung. ET uses 2D projection images from many different tomographic reconstructions provide information at a resolution viewing angles to reconstruct an object in three dimensions (13, better than 6 nm about the in situ arrangements of macromolecules 14). These researchers were able to identify major features of that are key for flagellar motility. We have visualized the hep- axonemes in the tomographic reconstructions of the 250-nm- tameric rings of the motor domains in the outer dynein arm thick sections, but at a resolution of Ϸ12 nm, detailed insights complex and determined that they lie parallel to the plane that into the molecular organization of the axoneme were not contains the axes of neighboring flagellar microtubules. Both the available. material associated with the central pair of microtubules and the Thanks to technological advances of the past decade, ET can radial spokes display a plane of symmetry that helps to explain the now be applied to relatively large, frozen-hydrated structures.
    [Show full text]
  • Formation and Structure of Filamentous Systems for Insect Flight and Mitotic Movements Melvyn Dennis Goode Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1967 Formation and structure of filamentous systems for insect flight and mitotic movements Melvyn Dennis Goode Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Genetics Commons Recommended Citation Goode, Melvyn Dennis, "Formation and structure of filamentous systems for insect flight and mitotic movements " (1967). Retrospective Theses and Dissertations. 3391. https://lib.dr.iastate.edu/rtd/3391 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. FORMATION AND STRUCTURE OF FILAMENTOUS SYSTEMS FOR INSECT FLIGHT AND MITOTIC MOVEMENTS by Melvyn Dennis Goode A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Cell Biology Approved: Signature was redacted for privacy. In Charge oi Major Work Signature was redacted for privacy. Chairman Advisory Committee Cell Biology Program Signature was redacted for privacy. Signature was redacted for privacy. Iowa State University Of Science and Technology Ames, Iowa: 1967 ii TABLE OF CONTENTS Page I. INTRODUCTION 1 PART ONE. THE MITOTIC APPARATUS OF A GIANT AMEBA 5 II. THE STRUCTURE AND PROPERTIES OF THE MITOTIC APPARATUS 6 A. Introduction .6 1. Early studies of mitosis 6 2. The mitotic spindle in living cells 7 3.
    [Show full text]
  • Ochromonas Mitochondria Contain a Specific Chloroplast Protein
    Proc. Nati. Acad. Sci. USA Vol. 82, pp. 1456-1459, March 1985 Cell Biology Ochromonas mitochondria contain a specific chloroplast protein (small subunit of ribulose-1,5-blsphosphate carboxylase/immunoelectron microscopy/chrysophycean alga/promiscuous DNA) GINETTE LACOSTE-ROYAL AND SARAH P. GIBBS Department of Biology, McGill University, Montreal, Quebec H3A iBi, Canada Communicated by Lynn Margulis, November 1, 1984 ABSTRACT Antibody raised against the small subunit of at 200C in Beijerinck's medium (15) at a light intensity of ribulose-1,5-bisphosphate carboxylase [3-phospho-D-glycerate 4300 lux. carboxy-lyase (dimerizing), EC 4.1.1.39] of Chlamydomonas Fixation and Embedding. Cells were fixed in 1% (vol/vol) reinhardtii labeled the mitochondria as well as the chloroplast glutaraldehyde in 0.1 M phosphate buffer for 90 min at 40C, of the chrysophyte alga Ochromonas danica in sections pre- rinsed in buffer and blocked in 2% (wt/vol) agar. The agar pared for immunoelectron microscopy by the protein A-gold blocks were dehydrated in 25% (vol/vol) ethanol at -50C, technique. The same antibody labeled the chloroplast but not then in 50%, 75%, and 95% ethanol at -18'C. Embedding the mitochondria of C. reinhardti. A quantitative study of la- was carried out at -18'C in Lowicryl K4M (16) according to beling in dark-grown, greening (32 hr light), and mature green the following schedule: 95% ethanol/resin, 1:1 (vol/vol), cells of 0. danica revealed that anti-small-subunit staining in overnight; 95% ethanol/resin, 1:2 (vol/vol), 2 times for 2 hr the mitochondria increased progressively in the light as it does each; pure resin, 2 hr and then overnight.
    [Show full text]
  • RSPH6A Is Required for Sperm Flagellum Formation and Male
    © 2018. Published by The Company of Biologists Ltd | Journal of Cell Science (2018) 131, jcs221648. doi:10.1242/jcs.221648 RESEARCH ARTICLE RSPH6A is required for sperm flagellum formation and male fertility in mice Ferheen Abbasi1,2,‡, Haruhiko Miyata1,‡, Keisuke Shimada1, Akane Morohoshi1,2, Kaori Nozawa1,2,*, Takafumi Matsumura1,3, Zoulan Xu1,3, Putri Pratiwi1 and Masahito Ikawa1,2,3,4,§ ABSTRACT (Carvalho-Santos et al., 2011) and is used for sensing and The flagellum is an evolutionarily conserved appendage used for locomotion. Mammalian spermatozoan flagella are highly sensing and locomotion. Its backbone is the axoneme and a specialized to carry male genetic material into the female component of the axoneme is the radial spoke (RS), a protein reproductive tract and fertilize the oocyte. Internal cross-sections ‘ ’ complex implicated in flagellar motility regulation. Numerous diseases show that the flagellum comprises a 9+2 microtubule structure: a occur if the axoneme is improperly formed, such as primary ciliary bundle of nine microtubule doublets that surround a central pair of dyskinesia (PCD) and infertility. Radial spoke head 6 homolog A single microtubules (Satir and Christensen, 2007). Called the (RSPH6A) is an ortholog of Chlamydomonas RSP6 in the RS head axoneme, this structure consists of macromolecular complexes such and is evolutionarily conserved. While some RS head proteins have as the outer and inner dynein arms and radial spokes (RSs) been linked to PCD, little is known about RSPH6A. Here, we show that (Fig. 1A). mouse RSPH6A is testis-enriched and localized in the flagellum. First characterized in sea urchins (Afzelius, 1959), the RS is a Rsph6a knockout (KO) male mice are infertile as a result of their short T-shaped protein complex that extends from the doublet immotile spermatozoa.
    [Show full text]
  • Direction of Sliding and Relative Sliding Velocities Within Trypsinized Sperm Axonemes of Gallus Domesticus
    Direction of sliding and relative sliding velocities within trypsinized sperm axonemes of Gallus domesticus DAVID M. WOOL LEY and ANDREW BRAMMALL* Department ofl'liysioloi>y. The Medical School, L'niversity of Bristol, Bristol BSS ITD, L'K •Present address: MRC Experimental Embryology and Teratology Unit, Medical Research Council Laboratories, Carshalton, Surrev SMS 4EF, UK Summary Trypsin digestion of demembranated fowl sper- orderly way by inter-doublet sliding. All the matozoa caused a longitudinal splitting of the doublets of the axoneme could be reactivated and distal part of the axoneme. The resulting strands, in all instances the direction of sliding was the consisting of groups of doublet microtubules, same as that reported for the cilia of Tetrahy- formed left-handed helices. On the evidence of tnena. Within the groups of doublets the electron micrographs, the digestion had caused measured inter-doublet displacements were gen- the loss of dynein arms from the outer row; it is erally similar, suggesting that the rates of sliding assumed that the doublets remained linked had been equivalent. These findings are con- together by dynein arms of the inner row. When trasted with the differential pattern of activation such helices were mechanically detached from that is assumed to occur in vivo. the proximal flagellum and reactivated with ad- Key words: Gallus domestic/is, sperm axonemes, sliding enosine triphosphate, they lengthened in an velocity. Introduction We have therefore made use of these preparations to study two aspects of the sliding behaviour relevant to It is well established that the motion of eukaryotic cilia the question of control and coordination.
    [Show full text]
  • Microtubule Motors
    Microtubule Forces Kevin Slep Microtubules are a Dynamic Scaffold Microtubules in red, XMA215 family MT polymerase protein in green Some Microtubule Functions Cell Structure Polarized Motor Track (kinesins and dynein) Cilia structure (motile and sensory) Mitotic and meiotic spindle structure Cell polarity Coordinate cell motility with the F-actin network Architecture of Tubulin and the Microtubule α/β-Tubulin: The Microtubule Building Block Tubulin is a heterodimer composed of α and β tubulin α and β tubulin are each approximately • 55 kD and are structurally very similar to •each other. •Each tubulin binds GTP: The α GTP is non- exchangeable and the dimer is very stable, Kd = 10-10; the β GTP is exchangeable in the dimer The Microtubule Architecture Tubulin binds head-to-tail along + protofilaments, forming LONGITUDINAL interactions. Longitudinal interactions complete the active site for GTP hydrolysis 13 protofilaments form a hollow tube-the microtubule: 25 nm OD, 14 nm ID (protofilaments interact via LATERAL interactions) The MT is a left-handed helix with a seam, it rises 1.5 heterodimers per turn (α and β form lateral interactions) MTs are polar-they have a plus end and a minus end - The γTubulin Ring Complex (γTuRC) forms a lockwasher to nucleate MTs Axial view Side View γTuRC positions nucleated 13 γTubulins in a ring γTuRC attachment microtubule The Centrosome is a Microtubule Organizing Center (MTOC) rich in γTuRC MTOC’s control where microtubules are formed Centrosomes contain peri-centrosomal material (PCM) surrounding a pair of centrioles γTuRC nucleation complexes are localized to the PCM Centrioles within centrosomes become basal bodies, which are nucleation centers for cilia (motile and primary) and flagella Centrosomes duplicate once per cell cycle Mother centriole nucleates growth of a daughter centriole with an orthogonal orientation Microtubule Polarity and Dynamics Polarized Microtubule Organization in Vivo Centrosome + + + + + + + + + Interphase Mitosis Microtubules are Dynamic Fish melanophore injected with Cy3-tubulin Vorobjev, I.A.
    [Show full text]