The plant plasma membrane proton pump ATPase: a highly regulated P-type ATPase with multiple physiological roles.
Around 40 P-type ATPases have been identified in Arabidopsis and rice, for which the genomes are known. None seems to exchange sodium and potassium, as does the animal Na(+)/K(+)-ATPase. Instead, plants, together with fungi, possess a proton pumping ATPase (H(+)-ATPase), which couples ATP hydrolysis to proton transport out of the cell, and so establishes an electrochemical gradient across the plasma membrane, which is dissipated by secondary transporters using protons in symport or antiport, as sodium is used in animal cells. Additional functions, such as stomata opening, cell growth, and intracellular pH homeostasis, have been proposed. Crystallographic data and homology modeling suggest that the H(+)-ATPase has a broadly similar structure to the other P-type ATPases but has an extended C-terminal region, which is involved in enzyme regulation. Phosphorylation of the penultimate residue, a Thr, and the subsequent binding of regulatory 14-3-3 proteins result in the formation of a dodecamer (six H(+)-ATPase and six 14-3-3 molecules) and enzyme activation. This type of regulation is unique to the P-type ATPase family. However, the recent identification of additional phosphorylated residues suggests further regulatory features.
Duby
Geoffrey
G
Unité de Biochimie Physiologique, Institut des Sciences de la Vie, Université Catholique de Louvain, 1348 Louvain-La-Neuve, Belgium.
Boutry
Marc
M
D048948:14-3-3 Proteins / Q000737:chemistry / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000201:enzymology*; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017494:Proton Pumps / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
D048948:14-3-3 Proteins; D007527:Isoenzymes; D010940:Plant Proteins; D017494:Proton Pumps; D000251:Adenosine Triphosphatases