Microtubule dynamic instability: numerical simulation of microtubule transition properties using a Lateral Cap model

1990 ◽  
Vol 95 (1) ◽  
pp. 33-48
Author(s):  
P.M. Bayley ◽  
M.J. Schilstra ◽  
S.R. Martin
Keyword(s):  
Dynamic Instability ◽  
Single Layer ◽  
Nucleotide Composition ◽  
General Mechanism ◽  
Gtp Hydrolysis ◽  
Complex Behaviour ◽  
Cap Model ◽  
Numerical Formulation ◽  
Dynamic Population ◽  
Hydrolysis Of

We present a numerical formulation for the dynamic instability of microtubules involving the stabilisation of growing microtubules by a single layer of tubulin-GTP, with GTP hydrolysis effectively coupled to tubulin-GTP addition. This Lateral Cap model provides a readily visualised, working mechanism for the co-existence and interconversion of growing and shrinking microtubules. This class of model is specified in terms of a hydrolysis rule, whereby the addition of tubulin-GTP causes hydrolysis of GTP on a previously terminal tubulin-GTP molecule as it becomes incorporated into the microtubule lattice. A specific formulation is illustrated, though this is not unique. A limited set of parameters defines the kinetics and affinity for tubulin-GTP at the binding sites at a given end of the microtubule. The rate constants are a function of the nucleotide composition of the binding site, principally comprising the two tubulin molecules, which interact laterally and longitudinally with the incoming tubulin-GTP molecule. The Lateral Cap formulation demonstrates that a single terminal layer of tubulin-GTP is sufficient to reproduce the apparently complex behaviour of a dynamic population of microtubules. It differs significantly from the fluctuating tubulin-GTP cap model of Chen and Hill (1985). It gives a molecular description to the switching of individual microtubules between growing and shrinking states in terms of the composition of the multi-start terminal layer of the microtubule, and provides a general mechanism for the differential kinetic behaviour at opposite ends of dynamic microtubules. It reproduces the essential features of microtubule length excursions, and predicts detailed characteristics of microtubule dynamics, including the basis of the apparently cooperative nature of the transition behaviour as a function of the concentration of tubulin-GTP. It is readily amenable to further experimental test and refinement.

scholarly journals Dilution of individual microtubules observed in real time in vitro: evidence that cap size is small and independent of elongation rate.

1991 ◽  
Vol 114 (1) ◽  
pp. 73-81 ◽  
Author(s):  
R A Walker ◽  
N K Pryer ◽  
E D Salmon
Keyword(s):  
Dynamic Instability ◽  
Elongation Rate ◽  
Gtp Hydrolysis ◽  
Microtubule Stability ◽  
Assembly Mechanism ◽  
High Elongation ◽  
Microtubule Growth ◽  
Hydrolysis Of ◽  
Brain Tubulin

Although the mechanism of microtubule dynamic instability is thought to involve the hydrolysis of tubulin-bound GTP, the mechanism of GTP hydrolysis and the basis of microtubule stability are controversial. Video microscopy of individual microtubules and dilution protocols were used to examine the size and lifetime of the stabilizing cap. Purified porcine brain tubulin (7-23 microM) was assembled at 37 degrees C onto both ends of isolated sea urchin axoneme fragments in a miniature flow cell to give a 10-fold variation in elongation rate. The tubulin concentration in the region of microtubule growth could be diluted rapidly (by 84% within 3 s of the onset of dilution). Upon perfusion with buffer containing no tubulin, microtubules experienced a catastrophe (conversion from elongation to rapid shortening) within 4-6 s on average after dilution to 16% of the initial concentration, independent of the predilution rate of elongation and length. Based on extrapolation of catastrophe frequency to zero tubulin concentration, the estimated lifetime of the stable cap after infinite dilution was less than 3-4 s for plus and minus ends, much shorter than the approximately 200 s observed at steady state (Walker, R. A., E. T. O'Brien, N. K. Pryer, M. Soboeiro, W. A. Voter, H. P. Erickson, and E. D. Salmon. 1988. J. Cell Biol. 107:1437-1448.). We conclude that during elongation, both plus and minus ends are stabilized by a short region (approximately 200 dimers or less) and that the size of the stable cap is independent of 10-fold variation in elongation rate. These results eliminate models of dynamic instability which predict extensive "build-up" stabilizing caps and support models which constrain the cap to the elongating tip. We propose that the cell may take advantage of such an assembly mechanism by using "catastrophe factors" that can promote frequent catastrophe even at high elongation rates by transiently binding to microtubule ends and briefly inhibiting GTP-tubulin association.

scholarly journals Assembly of chick brain MAP2-tubulin microtubule protein. Analysis of tubulin subunit flux rates by immunofluorescence microscopy

1991 ◽  
Vol 277 (1) ◽  
pp. 245-253 ◽  
Author(s):  
M F Symmons ◽  
R G Burns
Keyword(s):  
Close Agreement ◽  
Immunofluorescence Microscopy ◽  
Dynamic Instability ◽  
Theoretical Models ◽  
Chick Brain ◽  
Gtp Hydrolysis ◽  
Tubulin Subunit ◽  
Microtubule Protein ◽  
Cap Model ◽  
Microscopy Method

A filter-based immunofluorescence-microscopy method for obtaining microtubule lengths has been developed and evaluated. Kinetic constants and mean lengths obtained show close agreement with those obtained by complementary methods applied to chick brain MAP2-tubulin microtubule protein in NaCl-supplemented buffer. The filter-based method has been used to estimate tubulin subunit flux (Jon) resulting from isothermal dilution of microtubule populations to various free tubulin concentrations, (c). This experimental Jon(c) plot is significantly different from that predicted by a variety of theoretical models, but is consistent with a ‘lateral cap’ model of dynamic instability [Bayley, Schilstra & Martin (1990) J. Cell. Sci. 95, 33-48] adapted to accommodate the observed vectorial GTP hydrolysis.

Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules

1988 ◽  
Vol 46 ◽  
pp. 122-123
Author(s):  
R.A Walker ◽  
S. Inoue ◽  
E.D. Salmon
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Abrupt Transition ◽  
Microtubule Associated Proteins ◽  
Asymmetrical Structure ◽  
Associated Proteins

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).

scholarly journals RASAL3 preferentially stimulates GTP hydrolysis of the Rho family small GTPase Rac2

2018 ◽  
Author(s):  
Yoonjae Shin ◽  
Yong Kim ◽  
Hyemin Kim ◽  
Nakyoung Shin ◽  
Tae Kim ◽  
...  
Keyword(s):  
Small Gtpase ◽  
Gtp Hydrolysis ◽  
Rho Family ◽  
Hydrolysis Of

Hydrolysis of Methoxylated Nickel Hydroxide Leading to Single-Layer Ni(OH)2 Nanosheets

2021 ◽  
Author(s):  
Keisuke Muramatsu ◽  
Yoshiyuki Kuroda ◽  
Hiroaki Wada ◽  
Atsushi Shimojima ◽  
Kazuyuki Kuroda
Keyword(s):  
Nickel Hydroxide ◽  
Single Layer ◽  
Hydrolysis Of

scholarly journals Synergistic Hydrolysis of Carboxymethyl Cellulose and Acid-Swollen Cellulose by Two Endoglucanases (CelZ and CelY) fromErwinia chrysanthemi

2000 ◽  
Vol 182 (20) ◽  
pp. 5676-5682 ◽  
Author(s):  
Shengde Zhou ◽  
Lonnie O. Ingram
Keyword(s):  
Carboxymethyl Cellulose ◽  
Cell Walls ◽  
Cellulase Activity ◽  
Substrate Preference ◽  
Erwinia Chrysanthemi ◽  
General Mechanism ◽  
Plant Cell Walls ◽  
Enzymatic Modification ◽  
Amorphous Cellulose ◽  
Hydrolysis Of

ABSTRACT Erwinia chrysanthemi produces a battery of hydrolases and lyases which are very effective in the maceration of plant cell walls. Although two endoglucanases (CelZ and CelY; formerly EGZ and EGY) are produced, CelZ represents approximately 95% of the total carboxymethyl cellulase activity. In this study, we have examined the effectiveness of CelY and CelZ alone and of combinations of both enzymes using carboxymethyl cellulose (CMC) and amorphous cellulose (acid-swollen cellulose) as substrates. Synergy was observed with both substrates. Maximal synergy (1.8-fold) was observed for combinations containing primarily CelZ; the ratio of enzyme activities produced was similar to those produced by cultures of E. chrysanthemi. CelY and CelZ were quite different in substrate preference. CelY was unable to hydrolyze soluble cellooligosaccharides (cellotetraose and cellopentaose) but hydrolyzed CMC to fragments averaging 10.7 glucosyl units. In contrast, CelZ readily hydrolyzed cellotetraose, cellopentaose, and amorphous cellulose to produce cellobiose and cellotriose as dominant products. CelZ hydrolyzed CMC to fragments averaging 3.6 glucosyl units. In combination, CelZ and CelY hydrolyzed CMC to products averaging 2.3 glucosyl units. Synergy did not require the simultaneous presence of both enzymes. Enzymatic modification of the substrate by CelY increased the rate and extent of hydrolysis by CelZ. Full synergy was retained by the sequential hydrolysis of CMC, provided CelY was used as the first enzyme. A general mechanism is proposed to explain the synergy between these two enzymes based primarily on differences in substrate preference.

scholarly journals Coordination of the leucine-sensing Rag GTPase cycle by leucyl-tRNA synthetase in the mTORC1 signaling pathway

2018 ◽  
Vol 115 (23) ◽  
pp. E5279-E5288 ◽  
Author(s):  
Minji Lee ◽  
Jong Hyun Kim ◽  
Ina Yoon ◽  
Chulho Lee ◽  
Mohammad Fallahi Sichani ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Trna Synthetase ◽  
Gtp Hydrolysis ◽  
Mtorc1 Signaling ◽  
Amino Acid Sensing ◽  
Gtpase Cycle ◽  
Rag Gtpase ◽  
Cancer Tissues ◽  
Mtorc1 Activation ◽  
Hydrolysis Of

A protein synthesis enzyme, leucyl-tRNA synthetase (LRS), serves as a leucine sensor for the mechanistic target of rapamycin complex 1 (mTORC1), which is a central effector for protein synthesis, metabolism, autophagy, and cell growth. However, its significance in mTORC1 signaling and cancer growth and its functional relationship with other suggested leucine signal mediators are not well-understood. Here we show the kinetics of the Rag GTPase cycle during leucine signaling and that LRS serves as an initiating “ON” switch via GTP hydrolysis of RagD that drives the entire Rag GTPase cycle, whereas Sestrin2 functions as an “OFF” switch by controlling GTP hydrolysis of RagB in the Rag GTPase–mTORC1 axis. The LRS–RagD axis showed a positive correlation with mTORC1 activity in cancer tissues and cells. The GTP–GDP cycle of the RagD–RagB pair, rather than the RagC–RagA pair, is critical for leucine-induced mTORC1 activation. The active RagD–RagB pair can overcome the absence of the RagC–RagA pair, but the opposite is not the case. This work suggests that the GTPase cycle of RagD–RagB coordinated by LRS and Sestrin2 is critical for controlling mTORC1 activation, and thus will extend the current understanding of the amino acid-sensing mechanism.

Mathematical modeling of microtubule dynamic instability: new insight into the link between gtp-hydrolysis and microtubule aging

2018 ◽  
Vol 52 (6) ◽  
pp. 2433-2456 ◽  
Author(s):  
Ayuna Barlukova ◽  
Diana White ◽  
Gérard Henry ◽  
Stéphane Honoré ◽  
Florence Hubert
Keyword(s):  
Dynamic Instability ◽  
Dynamic Properties ◽  
Model Parameters ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Unique Type ◽  
Microtubule Targeting Agents ◽  
Age Dependent ◽  
Type Of Behavior ◽  
Insight Into

Microtubules (MTs) are protein polymers that exhibit a unique type of behavior referred to as dynamic instability. That is, they undergo periods of growth (through the addition of GTP-tubulin) and shortening (through the subtraction of GDP-tubulin). Shortening events are very fast, where this transition is referred to as a catastrophe. There are many processes that regulate MT dynamic instability, however, recent experiments show that MT dynamics may be highly regulated by a MTs age, where young MTs are less likely to undergo shortening events than older ones. In this paper, we develop a novel modeling approach to describe how the age of a MT affects its dynamic properties. In particular, we extend on a previously developed model that describes MT dynamics, by proposing a new concept for GTP-tubulin hydrolysis (the process by which newly incorporated GTP-tubulin is hydrolyzed to lower energy GDP-tubulin). In particular, we assume that hydrolysis is mainly vectorial, age-dependent and delayed according to the GTP-tubulin incorporation into the MT. Through numerical simulation, we are able to show how MT age affects certain properties that define MT dynamics. For example, simulations illustrate how the aging process leads to an increase in the rate of GTP-tubulin hydrolysis for older MTs, as well as increases in catastrophe frequency. Also, since it has been found that MT dynamic instability is affected by chemotherapy microtubule-targeting agents (MTAs), we highlight the fact that our model can be used to investigate the action of MTAs on MT dynamics by varying certain model parameters.

scholarly journals Polarization of Diploid Daughter Cells Directed by Spatial Cues and GTP Hydrolysis of Cdc42 in Budding Yeast

PLoS ONE ◽  
2013 ◽  
Vol 8 (2) ◽  
pp. e56665 ◽  
Author(s):  
Wing-Cheong Lo ◽  
Mid Eum Lee ◽  
Monisha Narayan ◽  
Ching-Shan Chou ◽  
Hay-Oak Park
Keyword(s):  
Budding Yeast ◽  
Spatial Cues ◽  
Gtp Hydrolysis ◽  
Daughter Cells ◽  
Hydrolysis Of

Selenocysteine Inserting RNA Elements Modulate GTP Hydrolysis of Elongation Factor SelB†

Biochemistry ◽  
1998 ◽  
Vol 37 (3) ◽  
pp. 885-890 ◽  
Author(s):  
Alexander Hüttenhofer ◽  
August Böck
Keyword(s):  
Elongation Factor ◽  
Gtp Hydrolysis ◽  
Rna Elements ◽  
Hydrolysis Of
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