scholarly journals Can microtubule motors use every available track?

2018 ◽  
Vol 217 (12) ◽  
pp. 4055-4056
Author(s):  
Prachee Avasthi
Keyword(s):  
Cell Biol ◽  
Microtubule Motors ◽  
Flagellar Assembly ◽  
And Function

Flagellar assembly and function depend on cargo traveling via motors on microtubule doublets. Bertiaux, Mallet et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201805030) find that only a subset of available doublets are used for this transport in trypanosomes, leading to questions about how and why this is achieved.

scholarly journals Microtubule organization: A complex solution

2016 ◽  
Vol 213 (6) ◽  
pp. 609-612 ◽  
Author(s):  
Paul T. Conduit
Keyword(s):  
Complex Solution ◽  
Microtubule Nucleation ◽  
Microtubule Organization ◽  
Microtubule Organizing Centers ◽  
Cell Biol ◽  
Ring Complexes ◽  
And Function

Microtubule nucleation within cells is catalyzed by γ-tubulin ring complexes localized at specific microtubule-organizing centers. In this issue, Muroyama et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201601099) reveal heterogeneity in the composition and function of these complexes, with wide implications for how cells organize their microtubule arrays.

The axonemal microtubules of the Chlamydomonas flagellum differ in tubulin isoform content

1998 ◽  
Vol 111 (3) ◽  
pp. 313-320 ◽  
Author(s):  
K.A. Johnson
Keyword(s):  
Structure And Function ◽  
Post Translational Modification ◽  
Immunofluorescence Analysis ◽  
Central Pair ◽  
Alpha Tubulin ◽  
Microtubule Polymerization ◽  
Tubulin Isoforms ◽  
Flagellar Assembly ◽  
Tyrosinated Tubulin ◽  
And Function

Little is known of the molecular basis for the diversity of microtubule structure and function found within the eukaryotic flagellum. Antibodies that discriminate between tyrosinated alpha tubulin and post-translationally detyrosinated alpha tubulin were used to localize these complementary tubulin isoforms in flagella of the single-celled green alga Chlamydomonas reinhardtii. Immunofluorescence analysis of intact axonemes detected both isoforms along most of the lengths of flagella; however, each had a short distal zone rich in tyrosinated tubulin. Localizations on splayed axonemes revealed that the microtubules of the central-pair apparatus were rich in tyrosinated tubulin, while outer doublets contained a mixture of both isoforms. Immunoelectron analysis of individual outer doublets revealed that while tyrosinated tubulin was present in both A and B tubules, detyrosinated tubulin was largely confined to the wall of the B hemi-tubules. The absence of detyrosinated tubulin from the A tubules of the outer doublets and the microtubules of the central pair, both of which extend past the B hemi-tubules of the outer doublets in the flagellar tip, explained the appearance of a tyrosinated tubulin-rich distal zone on intact axonemes. Localizations performed on cells regenerating flagella revealed that flagellar assembly used tyrosinated tubulin; detyrosination of the B tubule occurred during later stages of regeneration, well after microtubule polymerization. The developmental timing of detyrosination, which occurs over a period during which the regrowing flagella begin to beat more effectively, suggests that post-translational modification of the B tubule surface may enhance dynein/B tubule interactions that power flagellar beating.

scholarly journals Diversification of Campylobacter jejuni Flagellar C-Ring Composition Impacts Its Structure and Function in Motility, Flagellar Assembly, and Cellular Processes

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Louie D. Henderson ◽  
Teige R. S. Matthews-Palmer ◽  
Connor J. Gulbronson ◽  
Deborah A. Ribardo ◽  
Morgan Beeby ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Content Type ◽  
Cellular Processes ◽  
Spatial Regulation ◽  
Flagellar Motors ◽  
Core Components ◽  
Flagellar Assembly ◽  
And Function ◽  
Conserved Core ◽  
Flagellar Biogenesis

ABSTRACT Bacterial flagella are reversible rotary motors that rotate external filaments for bacterial propulsion. Some flagellar motors have diversified by recruiting additional components that influence torque and rotation, but little is known about the possible diversification and evolution of core motor components. The mechanistic core of flagella is the cytoplasmic C ring, which functions as a rotor, directional switch, and assembly platform for the flagellar type III secretion system (fT3SS) ATPase. The C ring is composed of a ring of FliG proteins and a helical ring of surface presentation of antigen (SPOA) domains from the switch proteins FliM and one of two usually mutually exclusive paralogs, FliN or FliY. We investigated the composition, architecture, and function of the C ring of Campylobacter jejuni, which encodes FliG, FliM, and both FliY and FliN by a variety of interrogative approaches. We discovered a diversified C. jejuni C ring containing FliG, FliM, and both FliY, which functions as a classical FliN-like protein for flagellar assembly, and FliN, which has neofunctionalized into a structural role. Specific protein interactions drive the formation of a more complex heterooligomeric C. jejuni C-ring structure. We discovered that this complex C ring has additional cellular functions in polarly localizing FlhG for numerical regulation of flagellar biogenesis and spatial regulation of division. Furthermore, mutation of the C. jejuni C ring revealed a T3SS that was less dependent on its ATPase complex for assembly than were other systems. Our results highlight considerable evolved flagellar diversity that impacts motor output, biogenesis, and cellular processes in different species. IMPORTANCE The conserved core of bacterial flagellar motors reflects a shared evolutionary history that preserves the mechanisms essential for flagellar assembly, rotation, and directional switching. In this work, we describe an expanded and diversified set of core components in the Campylobacter jejuni flagellar C ring, the mechanistic core of the motor. Our work provides insight into how usually conserved core components may have diversified by gene duplication, enabling a division of labor of the ancestral protein between the two new proteins, acquisition of new roles in flagellar assembly and motility, and expansion of the function of the flagellum beyond motility, including spatial regulation of cell division and numerical control of flagellar biogenesis in C. jejuni. Our results highlight that relatively small changes, such as gene duplications, can have substantial ramifications on the cellular roles of a molecular machine.

scholarly journals The role of retrograde intraflagellar transport in flagellar assembly, maintenance, and function

2012 ◽  
Vol 199 (1) ◽  
pp. 151-167 ◽  
Author(s):  
Benjamin D. Engel ◽  
Hiroaki Ishikawa ◽  
Kimberly A. Wemmer ◽  
Stefan Geimer ◽  
Ken-ichi Wakabayashi ◽  
...  
Keyword(s):  
Intraflagellar Transport ◽  
Retrograde Transport ◽  
Full Length ◽  
Temperature Sensitive ◽  
Nonpermissive Temperature ◽  
Flagellar Beat ◽  
Flagellar Assembly ◽  
Ph Shock ◽  
And Function

The maintenance of flagellar length is believed to require both anterograde and retrograde intraflagellar transport (IFT). However, it is difficult to uncouple the functions of retrograde transport from anterograde, as null mutants in dynein heavy chain 1b (DHC1b) have stumpy flagella, demonstrating solely that retrograde IFT is required for flagellar assembly. We isolated a Chlamydomonas reinhardtii mutant (dhc1b-3) with a temperature-sensitive defect in DHC1b, enabling inducible inhibition of retrograde IFT in full-length flagella. Although dhc1b-3 flagella at the nonpermissive temperature (34°C) showed a dramatic reduction of retrograde IFT, they remained nearly full-length for many hours. However, dhc1b-3 cells at 34°C had strong defects in flagellar assembly after cell division or pH shock. Furthermore, dhc1b-3 cells displayed altered phototaxis and flagellar beat. Thus, robust retrograde IFT is required for flagellar assembly and function but is dispensable for the maintenance of flagellar length. Proteomic analysis of dhc1b-3 flagella revealed distinct classes of proteins that change in abundance when retrograde IFT is inhibited.

scholarly journals Reversal of the posttranslational modification on Chlamydomonas flagellar alpha-tubulin occurs during flagellar resorption.

1985 ◽  
Vol 100 (2) ◽  
pp. 457-462 ◽  
Author(s):  
S W L'Hernault ◽  
J L Rosenbaum
Keyword(s):  
Posttranslational Modification ◽  
Alpha Tubulin ◽  
Cell Biol ◽  
Control Step ◽  
Flagellar Assembly

We previously have shown that a posttranslational modification of alpha-tubulin takes place in the flagellum during Chlamydomonas flagellar assembly (L'Hernault, S. W., and J. L. Rosenbaum, 1983, J. Cell Biol., 97:258-263). In this report, we show that the posttranslationally modified alpha-3 tubulin is changed back to its unmodified alpha-1 precursor form during the microtubular disassembly that takes place during flagellar resorption. These data indicate that the addition and removal of a posttranslational modification on alpha-tubulin might be a control step in the assembly and disassembly of flagella.

scholarly journals Domain Analysis of the FliM Protein ofEscherichia coli

1998 ◽  
Vol 180 (21) ◽  
pp. 5580-5590 ◽  
Author(s):  
Michael A. A. Mathews ◽  
Hua Lucy Tang ◽  
David F. Blair
Keyword(s):  
Sequence Similarity ◽  
Flagellar Motor ◽  
Binding Studies ◽  
Phosphorylated Protein ◽  
Cell Lysates ◽  
Terminal Domain ◽  
Flagellar Assembly ◽  
Flagellar Proteins ◽  
And Function ◽  
Multiple Domains

ABSTRACT The FliM protein of Escherichia coli is required for the assembly and function of flagella. Genetic analyses and binding studies have shown that FliM interacts with several other flagellar proteins, including FliN, FliG, phosphorylated CheY, other copies of FliM, and possibly MotA and FliF. Here, we examine the effects of a set of linker insertions and partial deletions in FliM on its binding to FliN, FliG, CheY, and phospho-CheY and on its functions in flagellar assembly and rotation. The results suggest that FliM is organized into multiple domains. A C-terminal domain of about 90 residues binds to FliN in coprecipitation experiments, is most stable when coexpressed with FliN, and has some sequence similarity to FliN. This C-terminal domain is joined to the rest of FliM by a segment (residues 237 to 247) that is poorly conserved, tolerates linker insertion, and may be an interdomain linker. Binding to FliG occurs through multiple segments of FliM, some in the C-terminal domain and others in an N-terminal domain of 144 residues. Binding of FliM to CheY and phospho-CheY was complex. In coprecipitation experiments using purified FliM, the protein bound weakly to unphosphorylated CheY and more strongly to phospho-CheY, in agreement with previous reports. By contrast, in experiments using FliM in fresh cell lysates, the protein bound to unphosphorylated CheY about as well as to phospho-CheY. Determinants for binding CheY occur both near the N terminus of FliM, which appears most important for binding to the phosphorylated protein, and in the C-terminal domain, which binds more strongly to unphosphorylated CheY. Several different deletions and linker insertions in FliM enhanced its binding to phospho-CheY in coprecipitation experiments with protein from cell lysates. This suggests that determinants for binding phospho-CheY may be partly masked in the FliM protein as it exists in the cytoplasm. A model is proposed for the arrangement and function of FliM domains in the flagellar motor.

scholarly journals Microtubule motors involved in nuclear movement during skeletal muscle differentiation

2017 ◽  
Vol 28 (7) ◽  
pp. 865-874 ◽  
Author(s):  
V. Gache ◽  
E. R. Gomes ◽  
B. Cadot
Keyword(s):  
Molecular Motors ◽  
Muscle Differentiation ◽  
Nuclear Movement ◽  
Nuclear Positioning ◽  
Cellular Processes ◽  
Nuclear Behavior ◽  
Microtubule Motors ◽  
Microtubule Motor ◽  
Motion Speed ◽  
And Function

Nuclear positioning is a determining event in several cellular processes, such as fertilization, cell migration, and cell differentiation. The structure and function of muscle cells, which contain hundreds of nuclei, have been shown to rely in part on proper nuclear positioning. Remarkably, in the course of muscle differentiation, nuclear movements along the myotube axis might represent the event required for the even positioning of nuclei in the mature myofiber. Here we analyze nuclear behavior, time in motion, speed, and alignment during myotube differentiation and temporal interference of cytoskeletal microtubule-related motors. Using specific inhibitors, we find that nuclear movement and alignment are microtubule dependent, with 19 microtubule motor proteins implicated in at least one nuclear behavior. We further focus on Kif1c, Kif5b, kif9, kif21b, and Kif1a, which affect nuclear alignment. These results emphasize the different roles of molecular motors in particular mechanisms.

scholarly journals Drosophila MIC60/mitofilin conducts dual roles in mitochondrial motility and crista structure

2017 ◽  
Vol 28 (24) ◽  
pp. 3471-3479 ◽  
Author(s):  
Pei-I Tsai ◽  
Amanda M. Papakyrikos ◽  
Chung-Han Hsieh ◽  
Xinnan Wang
Keyword(s):  
Neuromuscular Junctions ◽  
Cellular Level ◽  
Dual Roles ◽  
Protein Levels ◽  
Mitochondrial Homeostasis ◽  
Synaptic Structure ◽  
Microtubule Motors ◽  
Mitochondrial Motility ◽  
And Function

MIC60/mitofilin constitutes a hetero-oligomeric complex on the inner mitochondrial membranes to maintain crista structure. However, little is known about its physiological functions. Here, by characterizing Drosophila MIC60 mutants, we define its roles in vivo. We discover that MIC60 performs dual functions to maintain mitochondrial homeostasis. In addition to its canonical role in crista membrane structure, MIC60 regulates mitochondrial motility, likely by influencing protein levels of the outer mitochondrial membrane protein Miro that anchors mitochondria to the microtubule motors. Loss of MIC60 causes loss of Miro and mitochondrial arrest. At a cellular level, loss of MIC60 disrupts synaptic structure and function at the neuromuscular junctions. The dual roles of MIC60 in both mitochondrial crista structure and motility position it as a crucial player for cellular integrity and survival.

scholarly journals Requirements for Conversion of the Na+-Driven Flagellar Motor of Vibrio cholerae to the H+-Driven Motor of Escherichia coli

2000 ◽  
Vol 182 (15) ◽  
pp. 4234-4240 ◽  
Author(s):  
Khoosheh K. Gosink ◽  
Claudia C. Häse
Keyword(s):  
Escherichia Coli ◽  
Vibrio Cholerae ◽  
Proton Translocation ◽  
Specific Inhibitor ◽  
The Other ◽  
E Coli ◽  
Alkaline Conditions ◽  
Flagellar Assembly ◽  
And Function ◽  
Hybrid Motor

ABSTRACT Bacterial flagella are powered by a motor that converts a transmembrane electrochemical potential of either H+ or Na+ into mechanical work. In Escherichia coli, the MotA and MotB proteins form the stator and function in proton translocation, whereas the FliG protein is located on the rotor and is involved in flagellar assembly and torque generation. The sodium-driven polar flagella of Vibrio species contain homologs of MotA and MotB, called PomA and PomB, and also contain two other membrane proteins called MotX and MotY, which are essential for motor rotation and that might also function in ion conduction. Deletions inpomA, pomB, motX, ormotY in Vibrio cholerae resulted in a nonmotile phenotype, whereas deletion of fliG gave a nonflagellate phenotype. fliG genes on plasmids complementedfliG-null strains of the parent species but notfliG-null strains of the other species. FliG-null strains were complemented by chimeric FliG proteins in which the C-terminal domain came from the other species, however, implying that the C-terminal part of FliG can function in conjunction with the ion-translocating components of either species. A V. cholerae strain deleted of pomA, pomB,motX, and motY became weakly motile when theE. coli motA and motB genes were introduced on a plasmid. Like E. coli, but unlike wild-type V. cholerae, motility of some V. cholerae strains containing the hybrid motor was inhibited by the protonophore carbonyl cyanide m-chlorophenylhydrazone under neutral as well as alkaline conditions but not by the sodium motor-specific inhibitor phenamil. We conclude that the E. coli proton motor components MotA and MotB can function in place of the motor proteins ofV. cholerae and that the hybrid motors are driven by the proton motive force.

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