CA2-TRANSPORTING ATPASE(S) OF THE RETICULUM TYPE IN INTRACELLULAR MEMBRANES OF SACCHAROMYCES-CEREVISIAE - BIOCHEMICAL-IDENTIFICATION()

Several lines of evidence are presented to show that the Ca2+-ATPase a ctivity of total yeast membranes is due to the reticulum (R) type of C a2+-ATPase: (1) Neither calmodulin nor low concentrations of calmoduli n antagonists change Ca2+ uptake; (2) removal of plasma membranes (PM) following Con A treatment of spheroplasts (SP) does not significantly alter Ca2+ uptake by the remaining membranes, but increases its speci fic activity 3.5-fold; (3) after incubation of membranes with [gamma-P -32]ATP, SDS-PAGE shows the formation of acyl phosphate intermediates with molecular masses of around 100, 180-190 and 205 kDa; formation of these acyl phosphates requires Ca2+ and is blocked by cyclopiazonic a cid, La3+ ions and in the absence of Ca2+. The data on fractionation o f yeast membranes are consistent with the suggestion that both the ER and the Golgi are equipped with Ca2+-ATPase(s).