The structural basis of calcium transport by the calcium pump.
The sarcoplasmic reticulum Ca2+-ATPase, a P-type ATPase, has a critical role in muscle function and metabolism. Here we present functional studies and three new crystal structures of the rabbit skeletal muscle Ca2+-ATPase, representing the phosphoenzyme intermediates associated with Ca2+ binding, Ca2+ translocation and dephosphorylation, that are based on complexes with a functional ATP analogue, beryllium fluoride and aluminium fluoride, respectively. The structures complete the cycle of nucleotide binding and cation transport of Ca2+-ATPase. Phosphorylation of the enzyme triggers the onset of a conformational change that leads to the opening of a luminal exit pathway defined by the transmembrane segments M1 through M6, which represent the canonical membrane domain of P-type pumps. Ca2+ release is promoted by translocation of the M4 helix, exposing Glu 309, Glu 771 and Asn 796 to the lumen. The mechanism explains how P-type ATPases are able to form the steep electrochemical gradients required for key functions in eukaryotic cells.
Olesen
Claus
C
Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, University of Aarhus, Ole Worms Alle, blg. 1185, DK - 8000 Aarhus C, Denmark.
Picard
Martin
M
Winther
Anne-Marie Lund
AM
Gyrup
Claus
C
Morth
J Preben
JP
Oxvig
Claus
C
Møller
Jesper Vuust
JV
Nissen
Poul
P
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001608:Beryllium; D002118:Calcium / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005459:Fluorides; D017136:Ion Transport; D013058:Mass Spectrometry; D008958:Models, Molecular; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D011817:Rabbits; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D019284:Thapsigargin
C035982:beryllium fluoride; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D001608:Beryllium; D005459:Fluorides; D002118:Calcium