title: Protein kinase A (PKA) phosphorylation of Na+/K+-ATPase opens intracellular C-terminal water pathway leading to third Na+-binding site in molecular dynamics simulations.
abstract: Phosphorylation is one of the major mechanisms for posttranscriptional modification of proteins. The addition of a compact, negatively charged moiety to a protein can significantly change its function and localization by affecting its structure and interaction network. We have used all-atom Molecular Dynamics simulations to investigate the structural consequences of phosphorylating the Na(+)/K(+)-ATPase (NKA) residue Ser(936), which is the best characterized phosphorylation site in NKA, targeted in vivo by protein kinase A (PKA). The Molecular Dynamics simulations suggest that Ser(936) phosphorylation opens a C-terminal hydrated pathway leading to Asp(926), a transmembrane residue proposed to form part of the third sodium ion-binding site. Simulations of a S936E mutant form, for which only subtle effects are observed when expressed in Xenopus oocytes and studied with electrophysiology, does not mimic the effects of Ser(936) phosphorylation. The results establish a structural association of Ser(936) with the C terminus of NKA and indicate that phosphorylation of Ser(936) can modulate pumping activity by changing the accessibility to the ion-binding site.
authors.affiliation: PUMPKIN-Centre for Membrane Pumps in Cells and Disease, Aarhus University, Aarhus 8000 C, Denmark.
authors.forename: Hanne
authors.initials: H
authors.lastname: Poulsen
authors.forename: Poul
authors.initials: P
authors.lastname: Nissen
authors.forename: Ole G
authors.initials: OG
authors.lastname: Mouritsen
authors.forename: Himanshu
authors.initials: H
authors.lastname: Khandelia
mesh_terms: D000818:Animals; D001665:Binding Sites; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005260:Female; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009154:Mutation; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013552:Swine; D014867:Water / Q000737:chemistry / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D021122:Protein Subunits; D014867:Water; D012964:Sodium; D017868:Cyclic AMP-Dependent Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase