title: Motion of the Ca2+-pump captured.
abstract: Studies of ion pumps, such as ATP synthetase and Ca(2+)-ATPase, have a long history. The crystal structures of several kinds of ion pump have been resolved, and provide static pictures of mechanisms of ion transport. In this study, using fast-scanning atomic force microscopy, we have visualized conformational changes in the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) in real time at the single-molecule level. The analyses of individual SERCA molecules in the presence of both ATP and free Ca(2+) revealed up-down structural changes corresponding to the Albers-Post scheme. This fluctuation was strongly affected by the ATP and Ca(2+) concentrations, and was prevented by an inhibitor, thapsigargin. Interestingly, at a physiological ATP concentrations, the up-down motion disappeared completely. These results indicate that SERCA does not transit through the shortest structure, and has a catalytic pathway different from the ordinary Albers-Post scheme under physiological conditions.
authors.affiliation: Kyoto University Graduate School of Biostudies, Kyoto, Japan. yokokawa@ims.tsukuba.ac.jp
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Yokokawa
authors.forename: Kunio
authors.initials: K
authors.lastname: Takeyasu
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D055162:Biocatalysis; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D003840:Deoxycholic Acid / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004800:Enzymes, Immobilized; D021621:Imaging, Three-Dimensional; D007700:Kinetics; D018625:Microscopy, Atomic Force; D018715:Microscopy, Video; D009124:Muscle Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D009994:Osmolar Concentration; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D059010:Single-Cell Analysis; D013501:Surface-Active Agents / Q000737:chemistry; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D004800:Enzymes, Immobilized; D009124:Muscle Proteins; D013501:Surface-Active Agents; D003840:Deoxycholic Acid; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium