scholarly journals Steady-state theory of the interference of GTP hydrolysis in the mechanism of microtubule assembly.

1983 ◽  
Vol 80 (23) ◽  
pp. 7234-7238 ◽  
Author(s):  
T. L. Hill ◽  
M. F. Carlier
Keyword(s):  
Steady State ◽  
State Theory ◽  
Microtubule Assembly ◽  
Gtp Hydrolysis

Concerning the location of the GTP hydrolysis site on microtubules

1985 ◽  
Vol 63 (6) ◽  
pp. 422-429 ◽  
Author(s):  
Michael Caplow ◽  
John Shanks ◽  
Bruna Pegoraro Brylawski
Keyword(s):  
Steady State ◽  
Reaction Scheme ◽  
Product Inhibition ◽  
Microtubule Assembly ◽  
Assembly Process ◽  
Progressive Decrease ◽  
Reaction Conditions ◽  
Gtp Hydrolysis ◽  
Tubulin Subunit ◽  
A Site

The kinetics for GTP hydrolysis associated with microtubule assembly with microtubular protein has been analyzed under reaction conditions where tubulin–GDP does not readily assemble into microtubules. The GTPase rate is only slightly faster during the time when net microtubule assembly occurs, as compared with steady state. The slightly slower steady-state GTPase rate apparently results from GDP product inhibition, since the progressive decrease in the rate can be quantitatively accounted for using the previously determined GTP dissociation constant and the Ki value for GDP. Since the GTPase rate is not a function of the rate for net microtubule assembly, it is concluded that GTP hydrolysis is not required for tubulin subunit incorporation into microtubules. The constancy of the rate indicates that the GTPase reaction occurs at a site, the concentration of which does not change during the assembly process. This result is consistent with a reaction scheme in which GTP hydrolysis occurs primarily at microtubule ends. We propose that hydrolysis occurs at microtubule ends, at the interface between a long core of tubulin–GDP subunits and a short cap of tubulin–GTP subunits.

Non-steady-state stimulated scattering: a convenient solution in terms of convolution integrals

1977 ◽  
Vol 352 (1671) ◽  
pp. 539-555
Keyword(s):  
Steady State ◽  
Input Pulse ◽  
State Theory ◽  
Spatial Modulation ◽  
Bragg Angle ◽  
Stimulated Scattering ◽  
Scattering Spectrum ◽  
Convolution Integrals ◽  
Beam Incident ◽  
Scattered Beam

A non-steady-state theory of stimulated light scattering, which places particular emphasis on the effects induced in the scattering medium, is developed. It is shown that a spatial modulation of the dielectric constant is induced whose amplitude and phase can be expressed in terms of simple convolution integrals. These involve only the input pulse shape, the steady-state scattering spectrum and the frequency shift between the laser and scattered beams. The effect of the induced modulation on the scattered beam and on any weak independent beam incident at the Bragg angle is also considered.

scholarly journals Dissociation of the Tubulin-sequestering and Microtubule Catastrophe-promoting Activities of Oncoprotein 18/Stathmin

1999 ◽  
Vol 10 (1) ◽  
pp. 105-118 ◽  
Author(s):  
Bonnie Howell ◽  
Niklas Larsson ◽  
Martin Gullberg ◽  
Lynne Cassimeris
Keyword(s):  
Tight Binding ◽  
Terminal Region ◽  
Microtubule Assembly ◽  
Gtp Hydrolysis ◽  
Truncated Protein ◽  
C Terminus ◽  
Dependent Change ◽  
Tubulin Subunit ◽  
Oncoprotein 18

Oncoprotein 18/stathmin (Op18) has been identified recently as a protein that destabilizes microtubules, but the mechanism of destabilization is currently controversial. Based on in vitro microtubule assembly assays, evidence has been presented supporting conflicting destabilization models of either tubulin sequestration or promotion of microtubule catastrophes. We found that Op18 can destabilize microtubules by both of these mechanisms and that these activities can be dissociated by changing pH. At pH 6.8, Op18 slowed microtubule elongation and increased catastrophes at both plus and minus ends, consistent with a tubulin-sequestering activity. In contrast, at pH 7.5, Op18 promoted microtubule catastrophes, particularly at plus ends, with little effect on elongation rates at either microtubule end. Dissociation of tubulin-sequestering and catastrophe-promoting activities of Op18 was further demonstrated by analysis of truncated Op18 derivatives. Lack of a C-terminal region of Op18 (aa 100–147) resulted in a truncated protein that lost sequestering activity at pH 6.8 but retained catastrophe-promoting activity. In contrast, lack of an N-terminal region of Op18 (aa 5–25) resulted in a truncated protein that still sequestered tubulin at pH 6.8 but was unable to promote catastrophes at pH 7.5. At pH 6.8, both the full length and the N-terminal–truncated Op18 bound tubulin, whereas truncation at the C-terminus resulted in a pronounced decrease in tubulin binding. Based on these results, and a previous study documenting a pH-dependent change in binding affinity between Op18 and tubulin, it is likely that tubulin sequestering observed at lower pH resulted from the relatively tight interaction between Op18 and tubulin and that this tight binding requires the C-terminus of Op18; however, under conditions in which Op18 binds weakly to tubulin (pH 7.5), Op18 stimulated catastrophes without altering tubulin subunit association or dissociation rates, and Op18 did not depolymerize microtubules capped with guanylyl (α, β)-methylene diphosphonate–tubulin subunits. We hypothesize that weak binding between Op18 and tubulin results in free Op18, which is available to interact with microtubule ends and thereby promote catastrophes by a mechanism that likely involves GTP hydrolysis.

scholarly journals The Steady-State Theory of the Expanding Universe

1948 ◽  
Vol 108 (3) ◽  
pp. 252-270 ◽  
Author(s):  
H. Bondi ◽  
T. Gold
Keyword(s):  
Steady State ◽  
State Theory ◽  
Expanding Universe

Steady-state theory of thermal explosions

1978 ◽  
Vol 14 (5) ◽  
pp. 658-660 ◽  
Author(s):  
E. A. Eremin ◽  
A. K. Kolesnikov
Keyword(s):  
Steady State ◽  
State Theory ◽  
Thermal Explosions

A Note on the General Steady-state Theory of Linear Magnetrons

1962 ◽  
Vol 12 (3) ◽  
pp. 243-246 ◽  
Author(s):  
A. W. HORSLEY ◽  
G. D. Sraisf
Keyword(s):  
Steady State ◽  
State Theory

scholarly journals Kinetics of GTP hydrolysis during the assembly of chick brain MAP2-tubulin microtubule protein

1991 ◽  
Vol 277 (1) ◽  
pp. 239-243 ◽  
Author(s):  
R G Burns
Keyword(s):  
Initial Rate ◽  
Molar Concentration ◽  
Microtubule Assembly ◽  
Chick Brain ◽  
Gtp Hydrolysis ◽  
Microtubule Protein ◽  
Rate Of Hydrolysis ◽  
Kinetics Of

The kinetics of GTP hydrolysis during microtubule assembly have been examined using chick brain MAP2-tubulin microtubule protein in a NaCl-supplemented buffer. The elongating microtubules terminate in a ‘GTP cap’, since the kinetics of GTP hydrolysis are slower than those of subunit addition. GTP hydrolysis is (a) stoichiometric, (b) occurs as a vectorial wave as the initial rate of hydrolysis is proportional to the molar concentration of microtubule ends and not to the initial rate of subunit addition, and (c) either does not occur, or occurs only at a much lower rate, in the terminal subunits.

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