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XB-ART-44995
J Biol Chem 2012 May 04;28719:15959-65. doi: 10.1074/jbc.M112.340406.
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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.

Poulsen H , Nissen P , Mouritsen OG , Khandelia H .


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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.

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Species referenced: Xenopus laevis

References [+] :
Andersson, Forskolin-induced down-regulation of Na+,K(+)-ATPase activity is not associated with internalization of the enzyme. 1998, Pubmed