scholarly journals The rates of formation and dissociation of actin-myosin complexes. Effects of solvent, temperature, nucleotide binding and head-head interactions

1982 ◽  
Vol 203 (2) ◽  
pp. 453-460 ◽  
Author(s):  
S B Marston
Keyword(s):  
Rate Constant ◽  
Protein Concentration ◽  
Order Rate Constant ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Light Scatter ◽  
Association Rate Constant ◽  
Heavy Meromyosin ◽  
Association Rate ◽  
Low Protein

The rates of formation and dissociation of actin-subfragment 1 and actin-heavy mero-myosin complexes were measured by using light-scatter and the change in fluorescence of N-iodoacetyl-N'-(5-sulpho-1-naphthyl)ethylenediamine (IAEDANS)-labelled acting as probes. Association rate measurements were made at low protein concentration, where the transients approximated to single exponentials with rate constants proportional to the concentration of reactant in excess. Dissociation rate measurements were made by displacing IAEDANS-actin from myosin with excess native actin and by a salt jump. The second-order rate constant of association for actin-subfragment 1 was 3 × 10(6) M-1 . s-1 in 60 mM-KCl at 13 degree C. It was decreased 10-fold in 500 mM-KCl and in 50% (v/v) glycol. It was decreased 6-fold when MgADP or Mg[beta gamma-imido]ATP bound to myosin. The dissociation rate constant was 0.012 s-1 in 60 mM-KCl at 13 degree C. It was increased 4-fold by 500 mM-KCl, 25-fold by 50% glycol, 8-fold by MgADP binding and 170-fold by Mg[beta gamma-imido]ATP binding. Ea for association was 70 kJ . mol-1 and for dissociation 35 kJ . mol-1. Heavy meromyosin associated at twice the rate observed for subfragment 1 and dissociated at less than one-twentieth of the rate for subfragment 1 (60 mM-KCl, 25 degree C), but when Mg[beta gamma-imido]ATP bound actin-heavy meromyosin dissociated at one-half the rate for subfragment 1. There were significant correlations between increase in the dissociation rate constant, decrease in binding constant and increase in magnitude of conformational change. The association rate constant did not correlate with any property of the actin-myosin complex.

scholarly journals Phalloidin enhances actin assembly by preventing monomer dissociation.

1984 ◽  
Vol 99 (2) ◽  
pp. 529-535 ◽  
Author(s):  
L M Coluccio ◽  
L G Tilney
Keyword(s):  
Rate Constant ◽  
Actin Filaments ◽  
Critical Concentration ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Muscle Actin ◽  
Actin Assembly ◽  
Association Rate Constant ◽  
Association Rate ◽  
Dissociation Rate Constants

Incubation of the isolated acrosomal bundles of Limulus sperm with skeletal muscle actin results in assembly of actin onto both ends of the bundles. These cross-linked bundles of actin filaments taper, thus allowing one to distinguish directly the preferred end for actin assembly from the nonpreferred end; the preferred end is thinner. Incubation with actin in the presence of equimolar phalloidin in 100 mM KCl, 1 mM MgCl2 and 0.5 mM ATP at pH 7.5 resulted in a slightly smaller association rate constant at the preferred end than in the absence of the drug (3.36 +/- 0.14 X 10(6) M-1 s-1 vs. 2.63 +/- 0.22 X 10(6) M-1 s-1, control vs. experimental). In the presence of phalloidin, the dissociation rate constant at the preferred end was reduced from 0.317 +/- 0.097 s-1 to essentially zero. Consequently, the critical concentration at the preferred end dropped from 0.10 microM to zero in the presence of the drug. There was no detectable change in the rate constant of association at the nonpreferred end in the presence of phalloidin (0.256 +/- 0.015 X 10(6) M-1 s-1 vs. 0.256 +/- 0.043 X 10(6) M-1 s-1, control vs. experimental); however, the dissociation rate constant was reduced from 0.269 +/- 0.043 s-1 to essentially zero. Thus, the critical concentration at the nonpreferred end changed from 1.02 microM to zero in the presence of phalloidin. Dilution-induced depolymerization at both the preferred and nonpreferred ends was prevented in the presence of phalloidin. Thus, phalloidin enhances actin assembly by lowering the critical concentration at both ends of actin filaments, a consequence of reducing the dissociation rate constants at each end.

scholarly journals Differential changes in the association and dissociation rate constants for binding of cystatins to target proteinases occurring on N-terminal truncation of the inhibitors indicate that the interaction mechanism varies with different enzymes

1994 ◽  
Vol 299 (1) ◽  
pp. 219-225 ◽  
Author(s):  
I Björk ◽  
E Pol ◽  
E Raub-Segall ◽  
M Abrahamson ◽  
A D Rowan ◽  
...  
Keyword(s):  
Rate Constant ◽  
Cystatin C ◽  
Rate Constants ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Association Rate Constant ◽  
Association Rate ◽  
Human Cystatin C ◽  
Human Cystatin ◽  
Chicken Cystatin

The importance of the N-terminal region of human cystatin C or chicken cystatin for the kinetics of interactions of the inhibitors with four cysteine proteinases was characterized. The association rate constants for the binding of recombinant human cystatin C to papain, ficin, actinidin and recombinant rat cathepsin B were 1.1 x 10(7), 7.0 x 10(6), 2.4 x 10(6) and 1.4 x 10(6) M-1.s-1, whereas the corresponding dissociation rate constants were 1.3 x 10(-7), 9.2 x 10(-6), 4.6 x 10(-2) and 3.5 x 10(-4) s-1. N-Terminal truncation of the first ten residues of the inhibitor negligibly affected the association rate constant with papain or ficin, but increased the dissociation rate constant approx. 3 x 10(4)- to 2 x 10(6)-fold. In contrast, such truncation decreased the association rate constant with cathepsin B approx. 60-fold, while minimally affecting the dissociation rate constant. With actinidin, the truncated cystatin C had both an approx. 15-fold lower association rate constant and an approx. 15-fold higher dissociation rate constant than the intact inhibitor. Similar results were obtained for intact and N-terminally truncated chicken cystatin. The decreased affinity of human cystatin C or chicken cystatin for cysteine proteinases after removal of the N-terminal region is thus due to either a decreased association rate constant or an increased dissociation rate constant, or both, depending on the enzyme. This behaviour indicates that the contribution of the N-terminal segment of the two inhibitors to the interaction mechanism varies with the target proteinase as a result of structural differences in the active-site region of the enzyme.

scholarly journals Polymerization of ADP-actin.

1984 ◽  
Vol 99 (3) ◽  
pp. 769-777 ◽  
Author(s):  
T D Pollard
Keyword(s):  
Steady State ◽  
Rate Constant ◽  
Rate Constants ◽  
Actin Filaments ◽  
Dissociation Rate ◽  
Elongation Rate ◽  
Dissociation Rate Constant ◽  
Association Rate Constant ◽  
Association Rate ◽  
Critical Concentrations

Using hexokinase, glucose, and ATP to vary reversibly the concentrations of ADP and ATP in solution and bound to Acanthamoeba actin, I measured the relative critical concentrations and elongation rate constants for ATP-actin and ADP-actin in 50 mM KCl, 1 mM MgCl2, 1 mM EGTA, 0.1 mM nucleotide, 0.1 mM CaCl2, 10 mM imidazole, pH 7. By both steady-state and elongation rate methods, the critical concentrations are 0.1 microM for ATP-actin and 5 microM for ADP-actin. Consequently, a 5 microM solution of actin can be polymerized, depolymerized, and repolymerized by simply cycling from ATP to ADP and back to ATP. The critical concentrations differ, because the association rate constant is 10 times higher and the dissociation rate constant is five times lower for ATP-actin than ADP-actin. These results show that ATP-actin occupies both ends of actin filaments growing in ATP. The bound ATP must be split on internal subunits and the number of terminal subunits with bound ATP probably depends on the rate of growth.

scholarly journals Hemoglobin in Frankia, a Nitrogen-Fixing Actinomycete

2002 ◽  
Vol 68 (5) ◽  
pp. 2629-2631 ◽  
Author(s):  
John D. Tjepkema ◽  
Robert E. Cashon ◽  
Jason Beckwith ◽  
Christa R. Schwintzer
Keyword(s):  
Optical Absorption ◽  
Rate Constant ◽  
Dissociation Rate ◽  
Oxygen Binding ◽  
Association Rate Constant ◽  
Association Rate ◽  
Absorption Bands ◽  
Oxygen Dissociation ◽  
Equilibrium Oxygen ◽  
Strain Cci3

ABSTRACT Frankia strain CcI3 grown in culture produced a hemoglobin which had optical absorption bands typical of a hemoglobin and a molecular mass of 14.1 kDa. Its equilibrium oxygen binding constant was 274 nM, the oxygen dissociation rate constant was 56 s−1, and the oxygen association rate constant was 206 μM−1 s−1.

Velocity of O2 uptake by human red blood cells

1961 ◽  
Vol 16 (3) ◽  
pp. 511-516 ◽  
Author(s):  
N. C. Staub ◽  
J. M. Bishop ◽  
R. E. Forster
Keyword(s):  
Rate Constant ◽  
Intermediate Compound ◽  
Oxygen Electrode ◽  
Theoretical Explanation ◽  
Association Rate Constant ◽  
Association Rate ◽  
Human Red Blood Cells ◽  
Hemoglobin Saturation ◽  
Uptake Process ◽  
Normal Human

We have determined the over-all association rate constant, k'c, for the uptake of oxygen by normal human erythrocytes from 0% to 97% initial hemoglobin saturation at pH 7.4 and 37óC. With a modified Hartridge-Roughton rapid-reaction apparatus, we used a small oxygen electrode to follow the oxygen uptake process rather than using the usual photocolorimetric analytical methods. The value of k'c averages 164 mm-1 sec.-1 at 0% initial saturation, rises slowly to over 300 at 50%, and then climbs rapidly to over 1500 at 95%. The theoretical explanation for the increase in k-c with rising initial oxyhemoglobin saturation is based on the increasing prominence of the fourth chemical association rate constant, k-4, in the intermediate compound theory of Adair. It is known that k-4 is several times larger than any of the other three k–s. Submitted on December 19, 1960

scholarly journals Protein-ligand dissociation rate constant from all-atom simulation

2021 ◽  
Author(s):  
Ekaterina Maximova ◽  
Eugene Postnikov ◽  
Anastasia Lavrova ◽  
Vladimir Farafonov ◽  
Dmitry Nerukh
Keyword(s):  
Molecular Dynamics ◽  
Rate Constant ◽  
Md Simulations ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Zero Force ◽  
Ligand Dissociation ◽  
Random Acceleration

Abstract Dissociation of a ligand isoniazid from a protein catalase was investigated using all-atom Molecular Dynamics (MD) simulations. Random Acceleration MD (τ-RAMD) was used where a random artificial force applied to the ligand facilitates its dissociation. We have suggested an approach to extrapolate such obtained dissociation times to the zero-force limit that was never attempted before, thus allowing direct comparison with experimentally measured values. We have found that our calculated dissociation time was equal to 36.1 seconds with statistically significant values distributed in the interval 0.2-72.0 s, that quantitatively matches the experimental value of 50 ± 8 seconds despite the extrapolation over nine orders of magnitude in time.

The Association Rate Constant for Heme Binding to Globin Is Independent of Protein Structure†

Biochemistry ◽  
1996 ◽  
Vol 35 (35) ◽  
pp. 11293-11299 ◽  
Author(s):  
Mark S. Hargrove ◽  
Doug Barrick ◽  
John S. Olson
Keyword(s):  
Protein Structure ◽  
Rate Constant ◽  
Heme Binding ◽  
Association Rate Constant ◽  
Association Rate

scholarly journals A sequence-specific threading tetra-intercalator with an extremely slow dissociation rate constant

2011 ◽  
Vol 3 (11) ◽  
pp. 875-881 ◽  
Author(s):  
Garen G. Holman ◽  
Maha Zewail-Foote ◽  
Amy Rhoden Smith ◽  
Kenneth A. Johnson ◽  
Brent L. Iverson
Keyword(s):  
Rate Constant ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Slow Dissociation

scholarly journals Reversibility in radionuclide/bentonite bulk and colloidal ternary systems

2015 ◽  
Vol 79 (6) ◽  
pp. 1307-1315 ◽  
Author(s):  
Nick Sherriff ◽  
Ragiab Issa ◽  
Katherine Morris ◽  
Francis Livens ◽  
Sarah Heath ◽  
...  
Keyword(s):  
Rate Constant ◽  
Ethylenediaminetetraacetic Acid ◽  
Average Rate ◽  
Ternary Systems ◽  
Dissociation Rate ◽  
Convincing Evidence ◽  
Dissociation Rate Constant ◽  
Stage Process ◽  
Slow Dissociation ◽  
The Eu

AbstractTernary systems of 152Eu(III), bulk bentonite and ethylenediaminetetraacetic acid (EDTA) ([Eu] = 7.9 × 10–10 M; pH = 6.0–7.0) have been studied. Without EDTA, there was slow uptake in a two-stage process, with initial rapid sorption of Eu(III) (96%), followed by slower uptake of a much smaller fraction (3.0% over a period of one month). The reversibility of Eu(III) binding was tested by allowing Eu(III) to sorb to bentonite for 1–322 days. EDTA was added to the pre-equilibrated Eu bentonite systems at 0.01 M, a concentration that was sufficient to suppress sorption in a system where EDTA was present prior to the contact of Eu(III) with bentonite. A fraction of the Eu was released instantaneously (30–50%), but a significant amount remained bound. With time, the amount of Eu(III) retained by the bentonite reduced, with a slow fraction dissociation rate constant of approximately 4.3 × 10–8 s–1 (values in the range 2.2 × 10–8 – 1.0 × 10–7 s–1) for pre-equilibration times ≥7 days. Eventually, the amount of Eu(III) remaining bound to the bentonite was within error of that when EDTA was present prior to contact (4.5% ± 0.6), although in systems with pre-equilibration times >100 days, full release took up to 500 days. Europium interactions with colloidal bentonite were also studied, and the dissociation rate constant measured by a resin competition method. For the colloids, more Eu was found in the slowly dissociating fraction (60–70%), but the first-order dissociation rate constant was faster, with an average rate constant of 8.8 × 10–7 s–1 and a range of 7.7 × 10–7 –9.5 × 10–7 s–1. For both bulk and colloidal bentonite, although slow dissociation was observed for Eu(III), there was no convincing evidence for 'irreversible' binding.

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