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Ellipticity changes of the sarcoplasmic reticulum Ca 2+ ‐ATPase induced by cation binding and phosphorylation
Author(s) -
Girardet Jean-Luc,
Dupont Yves
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80413-b
Subject(s) - endoplasmic reticulum , chemistry , atpase , phosphorylation , circular dichroism , calcium , calcium atpase , enzyme , biophysics , covalent bond , crystallography , biochemistry , biology , organic chemistry
The sarcoplasmic reticulum (SR) Ca 2+ ‐ATPase is a member of the ‘P‐type’ class of cation transport ATPases which form a covalent phosphorylated intermediate. It has been proposed that during ion transport, these proteins cyclically adopt two major enzymatic states E 1 and E 2 , that are related to two essential conformations of the protein. By the use of especially sensitive circular dichroism (CD) instrumentation it is shown here that Ca 2+ addition induces 5% or 2.5% increases in Ca 2+ ‐ATPase ellipticity at 225 nm in the absence or in the presence of Mg 2+ , respectively. Furthermore, a 2% change in the same direction was observed when the enzyme was phosphorylated with P i in the absence of Ca 2+ . These results suggest that the E 1 ⇔ E 2 transition and the E 2 ‐P formation are associated with structural changes of the polypeptide backbone structure of the calcium pump protein.