Localization of a K+-binding Site Involved in Dephosphorylation of the Sarcoplasmic Reticulum Ca2+-ATPase

• Published in: The Journal of biological chemistry Vol. 279; no. 45; pp. 46355 - 46358
• Main Authors: Sørensen, Thomas Lykke-Møller, Clausen, Johannes D, Jensen, Anne-Marie Lund, Vilsen, Bente, Møller, Jesper Vuust, Andersen, Jens Peter, Nissen, Poul
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 05.11.2004
• Subjects: Adenosine Diphosphate - chemistry; Adenosine Triphosphatases - chemistry; Amino Acid Sequence; Animals; Binding Sites; Calcium-Transporting ATPases - metabolism; COS Cells; Crystallography, X-Ray; Cytoplasm - metabolism; DNA, Complementary - metabolism; Electrons; Glutamic Acid - chemistry; Models, Molecular; Molecular Sequence Data; Muscle, Skeletal - metabolism; Mutagenesis, Site-Directed; Mutation; Phosphorylation; Potassium - chemistry; Protein Conformation; Protein Structure, Tertiary; Protein Transport; Rabbits; Sarcoplasmic Reticulum - metabolism; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.C400414200

K + plays an important role for the function of the sarco(endo)plasmic reticulum Ca 2+ -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 Glu 732 define the K + /Rb + site in the Ca 2+ -ATPase conformation with bound Ca 2+ , ADP, and . Functional analysis of Ca 2+ -ATPase mutants with alterations to Glu 732 shows that this site is indeed important for the stimulatory effect of K + on the dephosphorylation rate. Comparison with the Ca 2+ -ATPase in a dephosphorylated E 2 conformation suggests that the K + site is involved in the correct movement and positioning of the A-domain during translocation and dephosphorylation.