Anion-sensitive, h-pumping ATPase in membrane vesicles from oat roots

Area of Science:

• Plant Physiology
• Membrane Transport
• Biochemistry

Background:

• Proton-pumping ATPases are crucial for maintaining cellular pH gradients.
• Understanding these pumps is vital for plant cell function and nutrient uptake.

Purpose of the Study:

• To characterize H(+)-pumping ATPases in oat root microsomal vesicles.
• To differentiate between various types of proton pumps based on their properties.

Main Methods:

• Utilized [(14)C]methylamine distribution and quinacrine fluorescent quenching to detect H(+)-pumping ATPases.
• Investigated the effects of Mg,ATP, inhibitors, and anions on proton pumping activity.
• Fractionated vesicles using density gradients to separate different ATPase activities.

Main Results:

• Identified Mg,ATP-dependent methylamine accumulation and quinacrine quench, indicating proton gradient formation.
• Characterized kinetic properties (K(m) for ATP) and sensitivities to inhibitors (N,N'-dicyclohexylcarbodiimide, vanadate).
• Demonstrated anion stimulation of H(+) pumping, with specific requirements for chloride.

Conclusions:

• Oat root membranes possess at least two distinct H(+)-pumping ATPases.
• A vanadate-sensitive ATPase is likely located in the plasma membrane.
• A vanadate-resistant, anion-sensitive ATPase exhibits characteristics of a vacuolar ATPase.