The Tiny Companion Matters: The Important Role of Protons in Active Transports in Plants

Abstract

In plants, the translocation of molecules, such as ions, metabolites, and hormones, between different subcellular compartments or different cells is achieved by transmembrane transporters, which play important roles in growth, development, and adaptation to the environment. To facilitate transport in a specific direction, active transporters that can translocate their substrates against the concentration gradient are needed. Examples of major active transporters in plants include ATP-binding cassette (ABC) transporters, multidrug and toxic compound extrusion (MATE) transporters, monosaccharide transporters (MSTs), sucrose transporters (SUTs), and amino acid transporters. Transport via ABC transporters is driven by ATP. The electrochemical gradient across the membrane energizes these secondary transporters. The pH in each cell and subcellular compartment is tightly regulated and yet highly dynamic, especially when under stress. Here, the effects of cellular and subcellular pH on the activities of ABC transporters, MATE transporters, MSTs, SUTs, and amino acid transporters will be discussed to enhance our understanding of their mechanics. The relation of the altered transporter activities to various biological processes of plants will also be addressed. Although most molecular transport research has focused on the substrate, the role of protons, the tiny counterparts of the substrate, should also not be ignored.

Membrane Proteins: Structure, Function and Motion

“…A molecular dynamics (MD) simulation study, based on the homology modelling with ANT, shows that the UCP2 structure is impermeable to water and possesses additional functional elements, such as a specific fatty-acid-binding site, which is related to the proton transport mechanism across the inner-mitochondrial membranes [11]. Proton transport is also the subject of a review article on the connection and importance of cellular and subcellular protons on the mechanism of activity of some molecule transporters essential for the biological processes in plants [12]. In a biophysical study on reconstituted archaerhodopsin photoreceptor protein, a proton pump, the real-time pore-forming properties of this protein is studied in bilayers [13].…”