H-pumping driven by the vanadate-sensitive ATPase in membrane vesicles from corn roots

Area of Science:

• Plant Physiology
• Biochemistry
• Membrane Transport

Background:

• Magnesium-adenosine triphosphate (Mg:ATP)-dependent proton (H(+))-pumping is crucial for plant cell function.
• Identifying specific H(+)-pumps in plant root membranes is essential for understanding nutrient uptake and cellular homeostasis.

Purpose of the Study:

• To isolate and characterize Mg:ATP-dependent H(+)-pumping activity in corn root membrane vesicles.
• To differentiate between various H(+)-pumping activities based on their sensitivity to inhibitors and density.

Main Methods:

• Utilized quinacrine fluorescence quenching to monitor H(+)-pumping rates.
• Employed linear sucrose density gradient centrifugation to separate membrane vesicles.
• Investigated inhibitor sensitivity (vanadate, nitrate) and kinetic parameters (ATP K(m), pH optimum).

Main Results:

• Two distinct H(+)-pumping activities were identified: one nitrate-sensitive and vanadate-resistant, the other nitrate-resistant and vanadate-sensitive.
• A membrane fraction enriched in vanadate-sensitive H(+)-pumping was obtained by KI washing.
• The vanadate-sensitive H(+)-pump exhibited kinetics and inhibitor sensitivity consistent with plasma membrane ATPase.

Conclusions:

• Corn root membranes contain distinct H(+)-pumping activities, including a vanadate-sensitive one likely representing the plasma membrane H(+)-ATPase.
• The characterized vanadate-sensitive H(+)-pump shares properties with those found in other plant species, suggesting conserved mechanisms.
• This study provides a method for isolating specific H(+)-pumping activities for further investigation into plant transport processes.