Potassium as an intrinsic uncoupler of the plasma membrane H+-ATPase.
The plant plasma membrane proton pump (H(+)-ATPase) is stimulated by potassium, but it has remained unclear whether potassium is actually transported by the pump or whether it serves other roles. We now show that K(+) is bound to the proton pump at a site involving Asp(617) in the cytoplasmic phosphorylation domain, from where it is unlikely to be transported. Binding of K(+) to this site can induce dephosphorylation of the phosphorylated E(1)P reaction cycle intermediate by a mechanism involving Glu(184) in the conserved TGES motif of the pump actuator domain. Our data identify K(+) as an intrinsic uncoupler of the proton pump and suggest a mechanism for control of the H(+)/ATP coupling ratio. K(+)-induced dephosphorylation of E(1)P may serve regulatory purposes and play a role in negative regulation of the transmembrane electrochemical gradient under cellular conditions where E(1)P is accumulating.
Buch-Pedersen
Morten J
MJ
Department of Plant Biology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark. mob@kvl.dk
Rudashevskaya
Elena L
EL
Berner
Torben S
TS
Venema
Kees
K
Palmgren
Michael G
MG
D000255:Adenosine Triphosphate / Q000378:metabolism; D002414:Cations, Monovalent; D002462:Cell Membrane / Q000201:enzymology; D006868:Hydrolysis; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*
D002414:Cations, Monovalent; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D011188:Potassium