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Mitochondrial F1-ATPase moiety from Phycomyces blakesleeanus: purification, characterization, and kinetic studies
J I de Vicente1, P del Valle, F Busto
1Departamento de Bioquímica y Biología Molecular, Universidad de León, Spain.
Abstract:
Mitochondrial F1-ATPase was purified from the mycelium of Phycomyces blakesleeanus NRRL 1555(-) and its kinetic characteristics were studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enzyme reveals five bands (alpha, beta, gamma, delta, and epsilon) characteristic of the F1 portion with apparent molecular weights of 60,000, 53,000, 31,000, 25,000, and 21,000, respectively. The molecular weight of the native F1-ATPase from Phycomyces blakesleeanus was in agreement with the stoichiometry alpha 3 beta 3 gamma delta epsilon. The MgATP complex is the true substrate for ATPase activity which has a Km value of 0.15 mM. High concentrations of free ATP or free Mg2+ ions inhibit the ATPase activity. ADP appears to act as a negative allosteric effector with regard to MgATP hydrolysis, with the apparent Vmax remaining unchanged.
Insights
Mitochondrial F1-adenosine triphosphatase (ATPase) from Phycomyces blakesleeanus was purified and characterized. Its kinetic properties reveal MgATP as the true substrate, with inhibition by excess free ATP or Mg2+ ions.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Mitochondrial F1-adenosine triphosphatase (ATPase) is crucial for cellular energy production.
- Understanding the kinetic properties of F1-ATPase from diverse organisms aids in elucidating its universal functions.
- Phycomyces blakesleeanus serves as a model organism for studying fungal biology and energy metabolism.
Purpose of the Study:
- To purify and characterize the mitochondrial F1-ATPase from Phycomyces blakesleeanus.
- To investigate the kinetic properties and substrate specificity of the purified enzyme.
- To determine the enzyme's subunit composition and stoichiometry.
Main Methods:
- Purification of F1-ATPase from Phycomyces blakesleeanus mycelium.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for subunit analysis.
- Kinetic assays to determine substrate affinity (Km) and inhibition patterns.
Main Results:
- Purified F1-ATPase exhibited five subunits (alpha, beta, gamma, delta, epsilon) with specific molecular weights.
- The native enzyme's molecular weight aligned with an alpha3 beta3 gamma delta epsilon stoichiometry.
- The MgATP complex was identified as the true substrate, with a Km of 0.15 mM.
- High concentrations of free ATP or Mg2+ inhibited activity, and ADP acted as a negative allosteric effector.
Conclusions:
- The study successfully purified and characterized Phycomyces blakesleeanus mitochondrial F1-ATPase.
- The enzyme's kinetic behavior, including substrate preference and allosteric regulation by ADP, was elucidated.
- Findings contribute to the understanding of F1-ATPase function and regulation in eukaryotic systems.