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Updated: Jun 16, 2026
14:44
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Characterizing metalloendonuclease mixed metal complexes by global kinetic analysis
Charulata B Prasannan1, Fuqian Xie, Cynthia M Dupureur
1Department of Chemistry and Biochemistry, Center for Nanoscience, University of Missouri St. Louis, St. Louis, MO 63121, USA.
Summary
Calcium ions (Ca(II)) do not directly stimulate PvuII endonuclease activity. Global kinetic analysis reveals that Ca(II) binds to a secondary site, forming a mixed-metal species with magnesium (Mg(II)) that has a similar cleavage rate to singly-magnesium-bound enzyme.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Metallonucleases often utilize multiple metal ions for catalytic activity.
- The role of secondary metal ions, such as calcium (Ca(II)), in metallonuclease mechanisms is often debated, with observed stimulation attributed to regulatory functions.
Purpose of the Study:
- To investigate the role of Ca(II) as a secondary metal ion in the PvuII endonuclease mechanism.
- To dissect the contributions of different metal ion-bound species to observed cleavage activity using global kinetic analysis.
Main Methods:
- Applied global kinetic analysis to cleavage data of PvuII endonuclease under varying Mg(II) and Ca(II) concentrations.
- Developed and tested kinetic models incorporating specific binding sites (A and B) for both Mg(II) and Ca(II), and various active species.
Main Results:
- Kinetic models best fit data when Ca(II) preferentially binds to the secondary (B) site, forming a mixed Mg(II)/Ca(II) enzyme species.
- This mixed-metal species exhibits a cleavage rate constant comparable to the singly Mg(II)-bound enzyme (approx. 0.01 s(-1)).
- Ca(II) alone does not stimulate PvuII endonuclease activity; simulated increases in activity at moderate Ca(II) concentrations are explained by the mixed-metal species' cleavage rate.
Conclusions:
- In PvuII endonuclease, Ca(II) acts as a secondary ion that binds to a distinct site, rather than directly stimulating activity.
- The observed Ca(II)-stimulated activity in some metallonucleases may be rationalized by the kinetic behavior of mixed-metal species, providing mechanistic insights not obtainable by other methods.
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