Reconstituted F1-ATPase complexes containing one impaired beta subunit are ATPase-active

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• F1-adenosine triphosphatase (ATPase) is a crucial enzyme complex responsible for ATP synthesis and hydrolysis.
• The enzyme's activity is regulated by its subunit composition, particularly the beta subunits.
• Understanding the functional contribution of individual subunits is key to elucidating the enzyme's mechanism.

Purpose of the Study:

• To investigate the impact of impaired beta subunits on the ATPase activity of F1-ATPase.
• To determine the minimum functional requirement of beta subunits for steady-state ATP hydrolysis.

Main Methods:

• Solid-phase reconstitution was used to create homogeneous populations of hybrid F1-ATPase complexes.
• Complexes were engineered with varying numbers (one, two, or three) of mutationally impaired beta subunits alongside wild-type beta subunits.
• ATPase activity assays were performed to measure the catalytic function of the reconstituted complexes.

Main Results:

• Hybrid F1-ATPase complexes with one impaired beta subunit and two wild-type beta subunits retained significant ATPase activity.
• Cooperative kinetics were observed in complexes with one impaired beta subunit, indicating functional interplay.
• Complexes containing two or three impaired beta subunits exhibited markedly reduced ATPase activity.

Conclusions:

• A single functional beta subunit within the F1-ATPase complex is sufficient to support substantial steady-state ATP hydrolysis.
• The presence of multiple impaired beta subunits significantly compromises the enzyme's catalytic efficiency.
• This suggests a degree of functional redundancy or a critical role for at least one functional beta subunit in catalysis.