Abstract
Membrane intrinsic transport systems play an important role in maintaining ion and pH homeostasis and forming the proton motive force in the cytoplasm and cell organelles. In most organisms, cation/proton antiporters (CPAs) mediate the exchange of K+, Na+ and Ca2+ for H+ across the membrane in response to a variety of environmental stimuli. The tertiary structure of the ion selective filter and the regulatory domains of Escherichia coli CPAs have been determined and a molecular mechanism of cation exchange has been proposed. Due to symbiogenesis, CPAs localized in mitochondria and chloroplasts of eukaryotic cells resemble prokaryotic CPAs. CPAs primarily contribute to keeping cytoplasmic Na+ concentrations low and controlling pH, which promotes the detoxification of electrophiles and formation of proton motive force across the membrane. CPAs in cyanobacteria and chloroplasts are regulators of photosynthesis and are essential for adaptation to high light or osmotic stress. CPAs in organellar membranes and in the plasma membrane also participate in various intracellular signal transduction pathways. This review discusses recent advances in our understanding of the role of CPAs in cyanobacteria and plant cells.
Highlights
The flux of cations and protons across membranes is a key process in maintaining intracellular ion homeostasis in various environments
Plants contain a large number of conserved cation/proton antiporters (CPAs) [19], which are localized in the plasma membrane and in the membranes of organelles such as vacuoles, endosomes and chloroplasts
We focus on the fundamental structure and physiological roles of CPAs in Escherichia coli, cyanobacteria and plant cells to evaluate their similarities and differences
Summary
The flux of cations and protons across membranes is a key process in maintaining intracellular ion homeostasis in various environments. A large number of ion transporters in the plasma membrane and in organellar membranes are involved in the regulation of ion translocation. They mediate the flux of potassium ions (K+), sodium ions (Na+) and protons (H+), common cations in cells and in the environment. The exchange of K+ or Na+ with H+ across cell membranes and organelles is coordinated by a variety of ion transporters. Plants contain a large number of conserved CPAs [19], which are localized in the plasma membrane and in the membranes of organelles such as vacuoles, endosomes and chloroplasts. We focus on the fundamental structure and physiological roles of CPAs in Escherichia coli, cyanobacteria and plant cells to evaluate their similarities and differences
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