Motion of the Ca2+-pump captured

FEBS J. 2011 Sep;278(17):3025-31. doi: 10.1111/j.1742-4658.2011.08222.x. Epub 2011 Jul 18.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism
  • Animals
  • Biocatalysis
  • Calcium / chemistry
  • Calcium / metabolism
  • Deoxycholic Acid / chemistry
  • Enzyme Inhibitors / pharmacology
  • Enzymes, Immobilized
  • Imaging, Three-Dimensional
  • Kinetics
  • Microscopy, Atomic Force
  • Microscopy, Video
  • Muscle Proteins / antagonists & inhibitors
  • Muscle Proteins / chemistry*
  • Muscle Proteins / metabolism*
  • Osmolar Concentration
  • Protein Conformation
  • Rabbits
  • Sarcoplasmic Reticulum / chemistry
  • Sarcoplasmic Reticulum / enzymology
  • Sarcoplasmic Reticulum / metabolism
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / antagonists & inhibitors
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / chemistry*
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism*
  • Single-Cell Analysis
  • Surface-Active Agents / chemistry
  • Thapsigargin / pharmacology

Substances

  • Enzyme Inhibitors
  • Enzymes, Immobilized
  • Muscle Proteins
  • Surface-Active Agents
  • Deoxycholic Acid
  • Thapsigargin
  • Adenosine Triphosphate
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium