H⁺-Translocating ATPases: Advances Using Membrane Vesicles

TLDR

Plant H⁺‑ATPases are studied in membrane vesicles, where plasma membrane and tonoplast types are detectable, enabling investigation of secondary transport systems driven by the proton electrochemical gradient. The study examines two primary plant H⁺‑ATPases using membrane vesicles as a simple experimental tool. Redox‑driven transport systems are studied directly in isolated vesicles, and identified proteins can be reconstituted into phospholipid vesicles for functional analysis. The study identifies a vanadate‑sensitive electrogenic H⁺‑ATPase at the plasma membrane and an anion‑sensitive electrogenic H⁺‑ATPase on the tonoplast, with pumping directions matching intact‑cell observations. The paper cites 154 references.

Abstract

In this paper, two primary active transport systems (H/sup +/ -ATPases) in plant cells are examined using membrane vesicles as a simple experimental tool. One electrogenic, H/sup +/ -translocating ATPase is vanadate-sensitive and associated with the plasma membrane. Another electrogenic, H/sup +/ -translocating ATPases is anion-sensitive, and localized on the tonoplast (and perhaps other membranes). According to the working model, the plasma membrane and tonoplast-type H/sup +/ -ATPases are detectable in inside-out plasma membrane and right-side-out tonoplast vesicles. The direction of H/sup +/ pumping into these vesicles would be consistent with the results from intact cells where H/sup +/ are extruded from the cell across the plasma membrane and pumped into the vacuole from the cytoplasm. Understanding the properties of H/sup +/ -pumping ATPases using membrane vesicles has paved the way for studies to identify secondary active transport systems coupled to the proton electrochemical gradient. Redox-driven transport systems can also be studied directly using the isolated vesicles. As transport proteins are identified, the functional activities can be specifically studied after reconstitution of the purified protein(s) into phospholipid membrane vesicles. 154 references.