title: Crystal structure of the calcium pump with a bound ATP analogue.
abstract: P-type ATPases are ATP-powered ion pumps that establish ion concentration gradients across cell and organelle membranes. Here, we describe the crystal structure of the Ca2+ pump of skeletal muscle sarcoplasmic reticulum, a representative member of the P-type ATPase superfamily, with an ATP analogue, a Mg2+ and two Ca2+ ions in the respective binding sites. In this state, the ATP analogue reorganizes the three cytoplasmic domains (A, N and P), which are widely separated without nucleotide, by directly bridging the N and P domains. The structure of the P-domain itself is altered by the binding of the ATP analogue and Mg2+. As a result, the A-domain is tilted so that one of the transmembrane helices moves to lock the cytoplasmic gate of the transmembrane Ca2+-binding sites. This appears to be the mechanism for occluding the bound Ca2+ ions, before releasing them into the lumen of the sarcoplasmic reticulum.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan. ct@iam.u-tokyo.ac.jp
authors.forename: Chikashi
authors.initials: C
authors.lastname: Toyoshima
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Mizutani
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism; D006860:Hydrogen Bonding; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000737:chemistry*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D014867:Water; C005147:5'-adenylyl (beta,gamma-methylene)diphosphonate; D000255:Adenosine Triphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium