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Effects of a Ca 2+ gradient and water activity on the phosphorylation of Ca 2+ ‐ATPase by P i
Author(s) -
Caldeira Maria Teresa,
de Meis Leopoldo
Publication year - 1991
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(91)80990-k
Subject(s) - pi , chemistry , dimethyl sulfoxide , endoplasmic reticulum , phosphorylation , atpase , enzyme , vesicle , membrane , biophysics , biochemistry , stereochemistry , biology , organic chemistry
The effects of dimethyl sulfoxide (20% v/v) on the phosphorylation of Ca 2+ ‐ATPase of the sarcoplasmic reticulum by P i vary depending on whether or not a Ca 2+ gradient is formed across the vesicle membranes. In the absence of a Ca 2+ gradient the solvent promotes a large increase in the affinity for P i . This increase is no longer observed after the formation of a Ca 2+ gradient. The enzyme affinity for Mg 2+ is practically the same in the presence and absence of a gradient. Addition of dimethyl sulfoxide leads to an increase of the enzyme affinity for Mg 2+ both in the presence and in the absence of a gradient.