title: Localization of a K+ -binding site involved in dephosphorylation of the sarcoplasmic reticulum Ca2+ -ATPase.
abstract: K+ plays an important role for the function of the sarco(endo)plasmic reticulum Ca2+ -ATPase (SERCA), but its binding site within the molecule has remained unidentified. We have located the binding site for a K+ ion in the P-domain by means of x-ray crystallography using crystals prepared in the presence of the K+ congener Rb+. Backbone carbonyls from the loop containing residues 711-715 together with the side chain of Glu732 define the K+/Rb+ site in the Ca2+ -ATPase conformation with bound Ca2+, ADP, and AlF4-. Functional analysis of Ca2+ -ATPase mutants with alterations to Glu732 shows that this site is indeed important for the stimulatory effect of K+ on the dephosphorylation rate. Comparison with the Ca2+ -ATPase in a dephosphorylated E2 conformation suggests that the K+ site is involved in the correct movement and positioning of the A-domain during translocation and dephosphorylation.
authors.affiliation: Centre for Structural Biology, Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
authors.forename: Thomas Lykke-Møller
authors.initials: TL
authors.lastname: Sørensen
authors.forename: Johannes D
authors.initials: JD
authors.lastname: Clausen
authors.forename: Anne-Marie Lund
authors.initials: AM
authors.lastname: Jensen
authors.forename: Bente
authors.initials: B
authors.lastname: Vilsen
authors.forename: Jesper Vuust
authors.initials: JV
authors.lastname: Møller
authors.forename: Jens Peter
authors.initials: JP
authors.lastname: Andersen
authors.forename: Poul
authors.initials: P
authors.lastname: Nissen
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D000251:Adenosine Triphosphatases / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004583:Electrons; D018698:Glutamic Acid / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010766:Phosphorylation; D011188:Potassium / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013997:Time Factors
chemical_list: D018076:DNA, Complementary; D018698:Glutamic Acid; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D011188:Potassium