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Roger Cooke – One of the best experts on this subject based on the ideXlab platform.

  • thermodynamic properties of the kinesin neck region docking to the catalytic core
    Biophysical Journal, 2003
    Co-Authors: Sarah E Rice, Y Cui, C V Sindelar, Nariman Naber, Marija Matuska, Ronald D Vale, Roger Cooke

    Abstract:

    Kinesin motors move on microtubules by a mechanism that involves a large, ATP-triggered conformational change in which a mechanical element called the neck linker docks onto the catalytic core, making contacts with the core throughout its length. Here, we investigate the thermodynamic properties of this conformational change using electron paramagnetic resonance (EPR) spectroscopy. We placed spin probes at several locations on the human kinesin neck linker and recorded EPR spectra in the presence of microtubules and either 5′-Adenylylimidodiphosphate (AMPPNP) or ADP at temperatures of 4–30°C. The free-energy change (ΔG) associated with AMPPNP-induced docking of the neck linker onto the catalytic core is favorable but small, about 3 kJ/mol. In contrast, the favorable enthalpy change (ΔH) and unfavorable entropy change (TΔS) are quite large, about 50 kJ/mol. A mutation in the neck linker, V331A/N332A, results in an unfavorable ΔG for AMPPNP-induced zipping of the neck linker onto the core and causes motility defects. These results suggest that the kinesin neck linker folds onto the core from a more unstructured state, thereby paying a large entropic cost and gaining a large amount of enthalpy.

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  • Thermodynamic properties of the kinesin neck-region docking to the catalytic core, Biophys
    , 2003
    Co-Authors: S. Rice, Y Cui, C V Sindelar, Nariman Naber, Marija Matuska, R. Vale, Roger Cooke

    Abstract:

    ABSTRACT Kinesin motors move onmicrotubules by amechanism that involves a large, ATP-triggered conformational change in which a mechanical element called the neck linker docks onto the catalytic core, making contacts with the core throughout its length. Here, we investigate the thermodynamic properties of this conformational change using electron paramagnetic resonance (EPR) spectroscopy. We placed spin probes at several locations on the human kinesin neck linker and recorded EPR spectra in the presence of microtubules and either 59-Adenylylimidodiphosphate (AMPPNP) or ADP at temperatures of 4–308C. The free-energy change (DG) associated with AMPPNP-induced docking of the neck linker onto the catalytic core is favorable but small, about 3 kJ/mol. In contrast, the favorable enthalpy change (DH) and unfavorable entropy change (TDS) are quite large, about 50 kJ/mol. A mutation in the neck linker, V331A/N332A, results in an unfavorable DG for AMPPNP-induced zipping of the neck linker onto the core and causes motility defects. These results suggest that the kinesin neck linker folds onto the core from a more unstructured state, thereby paying a large entropic cost and gaining a large amount of enthalpy

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Ferid Murad – One of the best experts on this subject based on the ideXlab platform.

  • mechanism of cyclic gmp inhibition of inositol phosphate formation in rat aorta segments and cultured bovine aortic smooth muscle cells
    Journal of Biological Chemistry, 1990
    Co-Authors: Masato Hirata, Klaus P Kohse, C H Chang, T Ikebe, Ferid Murad

    Abstract:

    Abstract In order to clarify the mechanism(s) by which cyclic GMP inhibits the generation of inositol phosphates in rat aorta segments and cultured bovine aortic smooth muscle cells, we studied phosphoinositide hydrolysis and GTPase activity in homogenates and membrane preparations of cultured bovine aortic smooth muscle cells. Pretreatment of homogenate preparations with cyclic GMP plus ATP did not inhibit [8-arginine, 3H] vasopressin (AVP) binding, but resulted in a total suppression of the AVP-induced GTPase activation. The pretreatment with cyclic GMP and ATP also inhibited the formation of inositol phosphates induced by AVP in the presence of low concentrations of guanosine 5′-(gamma-thio)triphosphate (GTP gamma S), or by high concentrations of GTP gamma S alone. However, the formation of inositol phosphates by high concentrations of Ca2+ alone was not blocked. These results suggest that the ability of cyclic GMP to inhibit phosphoinositide hydrolysis results from an inhibition of a guanine nucleotide regulatory protein activation, and the interaction between guanine nucleotide regulatory protein and phospholipase C. While the precise site of this inhibition is not presently known, the inhibition by cyclic GMP is dependent upon the addition of ATP and probably entails a phosphorylation event since Adenylylimidodiphosphate can not substitute for the ATP requirement.

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Uwe Panten – One of the best experts on this subject based on the ideXlab platform.

  • Identification of an ATP-sensitive K^+ channel in spiny neurons of rat caudate nucleus
    Pflügers Archiv, 1994
    Co-Authors: Christina Schwanstecher, Uwe Panten

    Abstract:

    On the somata of GABAergic spiny neurons in the caudate nucleus of the rat an ATP-sensitive K^+ channel (K_ATP-channel) was identified. The K_ATP-currents in cell-attached patches were activated both by energy-depleting conditions (200 μM cyanide) and by diazoxide (300 μM) and were reversibly blocked by tolbutamide (EC_50=5 μM). In inside-out patch membranes both ATP (1 mM) and its non-hydrolyzable analog AMP-PNP (Adenylylimidodiphosphate; EC_50=27μM) reversibly inhibited channel activity. These results demonstrate that the K_ATP-channel in spiny neurons displays properties characteristic of the K_ATP-channel in hippocampal, neocortical and nigral neurons and in pancreatic ß-cells.

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  • Identification of an ATP-sensitive K+ channel in spiny neurons of rat caudate nucleus.
    Pflügers Archiv: European Journal of Physiology, 1994
    Co-Authors: Christina Schwanstecher, Uwe Panten

    Abstract:

    On the somata of GABAergic spiny neurons in the caudate nucleus of the rat an ATP-sensitive K+ channel (KATP-channel) was identified. The KATP-currents in cell-attached patches were activated both by energy-depleting conditions (200 μM cyanide) and by diazoxide (300 μM) and were reversibly blocked by tolbutamide (EC50=5 μM). In inside-out patch membranes both ATP (1 mM) and its non-hydrolyzable analog AMP-PNP (Adenylylimidodiphosphate; EC50=27μM) reversibly inhibited channel activity. These results demonstrate that the KATP-channel in spiny neurons displays properties characteristic of the KATP-channel in hippocampal, neocortical and nigral neurons and in pancreatic s-cells.

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  • Identification of an ATP-sensitive K+ channel in spiny neurons of rat caudate nucleus.
    Pfl�gers Archiv European Journal of Physiology, 1994
    Co-Authors: Christina Schwanstecher, Uwe Panten

    Abstract:

    On the somata of GABAergic spiny neurons in the caudate nucleus of the rat an ATP-sensitive K+ channel (KATP-channel) was identified. The KATP-currents in cell-attached patches were activated both by energy-depleting conditions (200 microM cyanide) and by diazoxide (300 microM) and were reversibly blocked by tolbutamide (EC50 = 5 microM). In inside-out patch membranes both ATP (1 mM) and its non-hydrolyzable analog AMP-PNP (Adenylylimidodiphosphate; EC50 = 27 microM) reversibly inhibited channel activity. These results demonstrate that the KATP-channel in spiny neurons displays properties characteristic of the KATP-channel in hippocampal, neocortical and nigral neurons and in pancreatic beta-cells.

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