Thermodynamics of actin polymerization; influence of the tightly bound divalent cation and nucleotide
| Autor: | Lewis C. Gershman, James E. Estes, Henry J. Kinosian, Lynn A. Selden |
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| Rok vydání: | 1991 |
| Předmět: |
Cations
Divalent Polymers Inorganic chemistry Enthalpy Biophysics Fluorescence Polarization macromolecular substances Activation energy Biochemistry Divalent symbols.namesake Adenosine Triphosphate Reaction rate constant Structural Biology Magnesium Molecular Biology Magnesium ion chemistry.chemical_classification Arrhenius equation Nucleotides Temperature Polymer Actins Adenosine Diphosphate Crystallography chemistry Polymerization symbols Thermodynamics Calcium |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology. 1077:151-158 |
| ISSN: | 0167-4838 |
| DOI: | 10.1016/0167-4838(91)90052-2 |
| Popis: | Previous work by this laboratory has shown that the tightly bound divalent cation of actin affects the enthalpy of the polymerization reaction for ATP-actin (Selden et al. (1986) J. Muscle Res. Cell Motil. 7, 215-224). In the present study, we have measured the temperature dependence of polymerization for actin containing ATP or ADP as the bound nucleotide and Mg2+ or Ca2+ (Mg-actin or Ca-actin) as the tightly bound divalent cation. In contrast to the marked effect of the tightly bound divalent cation on enthalpy and entropy changes for the polymerization of ATP-actin, ADP-actin polymerization is affected very little by the tightly bound divalent cation. The Arrhenius and van't Hoff plots for polymerization of Ca-ATP-, Mg-ADP- and Ca-ADP-actin were found to be non-linear. The free energy data for actin polymerization have been analyzed as a second order function of absolute temperature (Osborne et al. (1976) Biochemistry 15, 317-320). The values of the enthalpy change and activation enthalpy change for Ca-ATP-, Mg-ADP- and Ca-ADP-actin polymerization were found to be temperature-dependent, in contrast to those for Mg-ATP-actin, which were nearly constant over the temperature range studied. These results suggest that (1) polymerization of actin which does not contain both Mg2+ and ATP may be a multi-step reaction including a rate-limiting step and (2) Mg-ATP-actin has a unique conformation which enhances its ability to polymerize. |
| Databáze: | OpenAIRE |
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