scholarly journals Presence of a new microtubule cold-stabilizing factor in bull sperm dynein preparations

1990 ◽  
Vol 270 (3) ◽  
pp. 821-824 ◽  
Author(s):  
J Eyer ◽  
D White ◽  
C Gagnon
Keyword(s):  
Active Site ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Bull Sperm ◽  
Cold Stability ◽  
Brain Tubulin

Brain tubulin polymerized with dynein isolated from bull spermatozoa forms cold-stable microtubules, in contrast with microtubules made of brain tubulin polymerized by brain microtubule-associated proteins (MAPs). The level of cold-stable microtubules depends on the concentration of dynein used. Addition of dynein to cold-unstable microtubules renders these microtubules stable to cold. Although ATP and a non-hydrolysable ATP analogue increase the formation of microtubules made of tubulin and dynein, these nucleotides have no effect on dynein cold-stabilizing properties. The data suggests that a new factor, not involving the dynein ATPase active site and present in bull sperm dynein preparations, confers cold-stability to microtubules.

scholarly journals Mechanical properties of brain tubulin and microtubules.

1988 ◽  
Vol 106 (4) ◽  
pp. 1205-1211 ◽  
Author(s):  
M Sato ◽  
W H Schwartz ◽  
S C Selden ◽  
T D Pollard
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Properties ◽  
Microtubule Assembly ◽  
Cross Link ◽  
Microtubule Associated Proteins ◽  
Heat Stable ◽  
Microtubule Protein ◽  
Associated Proteins ◽  
Steady Shearing ◽  
Brain Tubulin

We measured the elasticity and viscosity of brain tubulin solutions under various conditions with a cone and plate rheometer using both oscillatory and steady shearing modes. Microtubules composed of purified tubulin, purified tubulin with taxol and 3x cycled microtubule protein from pig, cow, and chicken behaved as mechanically indistinguishable viscoelastic materials. Microtubules composed of pure tubulin and heat stable microtubule-associated proteins were also similar but did not recover their mechanical properties after shearing like other samples, even after 60 min. All of the other microtubule samples were more rigid after flow orientation, suggesting that the mechanical properties of anisotropic arrays of microtubules may be substantially greater than those of randomly arranged microtubules. These experiments confirm that MAPs do not cross link microtubules. Surprisingly, under conditions where microtubule assembly is strongly inhibited (either 5 degrees or at 37 degrees C with colchicine or Ca++) tubulin was mechanically indistinguishable from microtubules at 10-20 microM concentration. By electron microscopy and ultracentrifugation these samples were devoid of microtubules or other obvious structures. However, these mechanical data are strong evidence that tubulin will spontaneously assemble into alternate structures (aggregates) in nonpolymerizing conditions. Because unpolymerized tubulin is found in significant quantities in the cytoplasm, it may contribute significantly to the viscoelastic properties of cytoplasm, especially at low deformation rates.

scholarly journals MAP6 is an intraluminal protein that induces neuronal microtubules to coil

2020 ◽  
Vol 6 (14) ◽  
pp. eaaz4344 ◽  
Author(s):  
Camille Cuveillier ◽  
Julie Delaroche ◽  
Maxime Seggio ◽  
Sylvie Gory-Fauré ◽  
Christophe Bosc ◽  
...  
Keyword(s):  
Nervous System ◽  
Mechanical Stress ◽  
Microtubule Associated Proteins ◽  
Left Handed ◽  
Neuronal Processes ◽  
Associated Proteins ◽  
The Face ◽  
Cold Stability

Neuronal activities depend heavily on microtubules, which shape neuronal processes and transport myriad molecules within them. Although constantly remodeled through growth and shrinkage events, neuronal microtubules must be sufficiently stable to maintain nervous system wiring. This stability is somehow maintained by various microtubule-associated proteins (MAPs), but little is known about how these proteins work. Here, we show that MAP6, previously known to confer cold stability to microtubules, promotes growth. More unexpectedly, MAP6 localizes in the lumen of microtubules, induces the microtubules to coil into a left-handed helix, and forms apertures in the lattice, likely to relieve mechanical stress. These features have not been seen in microtubules before and could play roles in maintaining axonal width or providing flexibility in the face of compressive forces during development.

scholarly journals Dynamic instability of individual microtubules analyzed by video light microscopy: rate constants and transition frequencies.

1988 ◽  
Vol 107 (4) ◽  
pp. 1437-1448 ◽  
Author(s):  
R A Walker ◽  
E T O'Brien ◽  
N K Pryer ◽  
M F Soboeiro ◽  
W A Voter ◽  
...  
Keyword(s):  
Rate Constants ◽  
Dynamic Instability ◽  
Dissociation Rate ◽  
Microtubule Associated Proteins ◽  
First Order ◽  
Associated Proteins ◽  
Dissociation Rate Constants ◽  
Elongation Phase ◽  
Association Rate Constants ◽  
Brain Tubulin

We have developed video microscopy methods to visualize the assembly and disassembly of individual microtubules at 33-ms intervals. Porcine brain tubulin, free of microtubule-associated proteins, was assembled onto axoneme fragments at 37 degrees C, and the dynamic behavior of the plus and minus ends of microtubules was analyzed for tubulin concentrations between 7 and 15.5 microM. Elongation and rapid shortening were distinctly different phases. At each end, the elongation phase was characterized by a second order association and a substantial first order dissociation reaction. Association rate constants were 8.9 and 4.3 microM-1 s-1 for the plus and minus ends, respectively; and the corresponding dissociation rate constants were 44 and 23 s-1. For both ends, the rate of tubulin dissociation equaled the rate of tubulin association at 5 microM. The rate of rapid shortening was similar at the two ends (plus = 733 s-1; minus = 915 s-1), and did not vary with tubulin concentration. Transitions between phases were abrupt and stochastic. As the tubulin concentration was increased, catastrophe frequency decreased at both ends, and rescue frequency increased dramatically at the minus end. This resulted in fewer rapid shortening phases at higher tubulin concentrations for both ends and shorter rapid shortening phases at the minus end. At each concentration, the frequency of catastrophe was slightly greater at the plus end, and the frequency of rescue was greater at the minus end. Our data demonstrate that microtubules assembled from pure tubulin undergo dynamic instability over a twofold range of tubulin concentrations, and that the dynamic instability of the plus and minus ends of microtubules can be significantly different. Our analysis indicates that this difference could produce treadmilling, and establishes general limits on the effectiveness of length redistribution as a measure of dynamic instability. Our results are consistent with the existence of a GTP cap during elongation, but are not consistent with existing GTP cap models.

scholarly journals The periodic association of MAP2 with brain microtubules in vitro.

1979 ◽  
Vol 80 (2) ◽  
pp. 266-276 ◽  
Author(s):  
H Kim ◽  
L I Binder ◽  
J L Rosenbaum
Keyword(s):  
Critical Concentration ◽  
Microtubule Assembly ◽  
Molar Ratio ◽  
Thin Sections ◽  
Microtubule Associated Proteins ◽  
Heat Stable ◽  
Associated Proteins ◽  
Brain Microtubules ◽  
Brain Tubulin

Several high molecular weight polypeptides have been shown to quantitatively copurify with brain tubulin during cycles of in vitro assembly-disassembly. These microtubule-associated proteins (MAPs) have been shown to influence the rate and extent of microtubule assembly in vitro. We report here that a heat-stable fraction highly enriched for one of the MAPs, MAP2 (mol wt approximately 300,000 daltons), devoid of MAP1 (mol wt approximately 350,000 daltons), has been purified from calf neurotubules. This MAP2 fraction stoichiometrically promotes microtubule assembly, lowering the critical concentration for tubulin assembly to 0.05 mg/ml. Microtubules saturated with MAP2 contain MAP2 and tubulin in a molar ratio of approximately 1 mole of MAP2 to 9 moles of tubulin dimer. Electron microscopy of thin sections of the MAP2-saturated microtubules fixed in the presence of tannic acid demonstrates a striking axial periodicity of 32 +/- 8 nm.

scholarly journals The cystoskeleton of unstimulated blood platelets: structure and composition of the isolated marginal microtubular band

1985 ◽  
Vol 78 (1) ◽  
pp. 1-22 ◽  
Author(s):  
D.M. Kenney ◽  
R.W. Linck
Keyword(s):  
Blood Platelets ◽  
Amorphous Material ◽  
Structural Units ◽  
Microtubule Associated Proteins ◽  
Major Structural Component ◽  
Associated Proteins ◽  
Amorphous Surface ◽  
Cytoskeletal System ◽  
Brain Tubulin ◽  
Dimensional Electrophoresis

Detergent-insoluble, marginal microtubular band (MB) cytoskeletons were isolated from unstimulated blood platelets after pretreatment with glycerol or with Taxol. MB cytoskeletons retained the shape of intact platelets and behaved in suspension as coherent structural units. The major structural component was a continuous coil of long microtubule(s), often with granular/amorphous material present in the centre; few typical actin filaments were observed. The coiled microtubules often had an amorphous surface coating, but no discrete inter-microtubule bridges were seen. Tubulin and actin (identified by immunochemical staining) were major polypeptides. None of the minor (greater than 10) polypeptide components comigrated with high molecular weight microtubule-associated proteins in brain tubulin. A novel polypeptide, resolved by two-dimensional electrophoresis and designated IEF-51K, was present in MB cytoskeletons in amounts approximately equivalent to each of the tubulin polypeptides. Evidence suggests that IEF-51K is a distinct, previously undescribed component of the platelet cytoskeletal system.

scholarly journals Developmental and comparative aspects of brine shrimp tubulin

1984 ◽  
Vol 219 (1) ◽  
pp. 137-148 ◽  
Author(s):  
T H Macrae ◽  
R F Ludueña
Keyword(s):  
Brine Shrimp ◽  
Peptide Mapping ◽  
Deae Cellulose ◽  
Bovine Brain ◽  
Two Dimensional Gel Electrophoresis ◽  
Microtubule Associated Proteins ◽  
Apparent Homogeneity ◽  
Associated Proteins ◽  
History Of ◽  
Brain Tubulin

Tubulin from embryos of the brine shrimp Artemia has been purified to apparent homogeneity by chromatography on phosphocellulose P11 and DEAE-cellulose, (NH4)2SO4 fractionation and assembly-disassembly of microtubules. Peptide mapping indicated that Artemia and bovine brain tubulin were very similar in spite of differences in the electrophoretic behaviour of tubulin from these two organisms. Isoelectric focusing and two-dimensional gel electrophoresis were used to resolve and identify several Artemia isotubulins . The isotubulin composition and the quantity of tubulin did not change during pre-emergence development of Artemia embryos. Formation of microtubules with tubulin purified from embryos at different stages of development did not require glycerol or microtubule-associated proteins and formation of structurally normal microtubules was actually hindered by glycerol and Mg2+. The characteristics of Artemia tubulin, in concert with the unusual life history of Artemia, suggest that this organism will be very useful for the study of tubulin gene expression and tubulin utilization during embryo development.

scholarly journals 270K microtubule-associated protein cross-reacting with anti-MAP2 IgG in the crayfish peripheral nerve axon.

1986 ◽  
Vol 103 (1) ◽  
pp. 33-39 ◽  
Author(s):  
N Hirokawa
Keyword(s):  
Cross Linking ◽  
Flexible Structure ◽  
High Molecular Weight Protein ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Weight Protein ◽  
The Cross ◽  
Cross Bridges ◽  
Brain Tubulin

MAPs (microtubule-associated proteins) were isolated from crayfish walking leg nerves. A major MAP was identified as a high molecular weight protein (270K). This protein co-migrated with mammalian MAP2, stimulated the polymerization of rat brain tubulin into microtubules, and was heat resistant. Rotary shadowing revealed that the 270K MAP is a long thin flexible structure. It formed cross-bridges of fine strands, linking microtubules with each other in vitro. These strands resemble the cross-bridges between microtubules observed in the crayfish axon permeabilized with saponin and quick-frozen, deep-etched. Antibodies against mammalian MAP2 cross-reacted with this crayfish MAP and stained the axoplasm of the walking leg nerves. Thus MAPs, especially the 270K MAP, appear to be a major component of the cross-linking strands between microtubules observed in the crayfish axon.

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