Effects of a Ca2+ gradient and water activity on the phosphorylation of Ca(2+)-ATPase by Pi.
The effects of dimethyl sulfoxide (20% v/v) on the phosphorylation of Ca(2+)-ATPase of the sarcoplasmic reticulum by Pi vary depending on whether or not a Ca2+ gradient is formed across the vesicle membranes. In the absence of a Ca2+ gradient the solvent promotes a large increase in the affinity for Pi. This increase is no longer observed after the formation of a Ca2+ gradient. The enzyme affinity for Mg2+ 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 Mg2+ both in the presence and in the absence of a gradient.
Caldeira
M T
MT
Departamento de Bioquímica, Universidade Federal do Rio de Janeiro, Brazil.
de Meis
L
L
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D010766:Phosphorylation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology*; D014617:Vacuoles / Q000378:metabolism; D014867:Water / Q000378:metabolism*
D010710:Phosphates; D014867:Water; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium; D004121:Dimethyl Sulfoxide