Independence of two conformations of sarcoplasmic reticulum Ca2+- ATPase molecules in hydrolyzing acetyl phosphate: A two model of the ATPase structural unit

Jun Nakamura, Genichi Tajima

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The sarcoplasmic reticulum Ca2+-ATPase molecules have been shown to exist in two conformations (A and B) that result from intermolecular interaction of ATPase molecules (Nakamura, J., and Tajima, G. (1995) J. Biol. Chem. 270, 17350-17354). The A form binds two calcium ions noncooperatively, whereas the B form binds the calcium ions cooperatively. Here, we examined the independence of these two forms in the calcium-activated hydrolysis of acetyl phosphate (AcP) under asynchronous and synchronous conditions of their E1-E2 transitions at 0-5 and 25 °C. Irrespective of their synchronism and temperature, the two forms hydrolyzed AcP due to calcium that was bound to each of the forms, indicating the independence of the two forms in hydrolyzing AcP. Taking into account the monomer-dimer transition of the ATPase molecules on the sarcoplasmic reticulum membrane accompanying E1-E2 transition of the molecules (Dux, L., Taylor, K. A, Ting-Beall, H. P., and Martonosi, A. (1985) J. Biol. Chem. 260, 11730-11743), the two types of molecules seem to independently carry out such monomer-dimer transition of the same type of molecules. Two pairs, each consisting of the same type of molecules, are suggested to be the structural unit of the ATPase molecules.

Original languageEnglish
Pages (from-to)19290-19294
Number of pages5
JournalJournal of Biological Chemistry
Volume272
Issue number31
DOIs
Publication statusPublished - 1997 Aug 1

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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