title: Potassium as an intrinsic uncoupler of the plasma membrane H+-ATPase.
abstract: 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.
authors.affiliation: Department of Plant Biology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark. mob@kvl.dk
authors.forename: Morten J
authors.initials: MJ
authors.lastname: Buch-Pedersen
authors.forename: Elena L
authors.initials: EL
authors.lastname: Rudashevskaya
authors.forename: Torben S
authors.initials: TS
authors.lastname: Berner
authors.forename: Kees
authors.initials: K
authors.lastname: Venema
authors.forename: Michael G
authors.initials: MG
authors.lastname: Palmgren
mesh_terms: 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*
chemical_list: D002414:Cations, Monovalent; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D011188:Potassium