Sarcoplasmic reticulum. IV. Solubilization of microsomal adenosine triphosphatase.

A soluble adenosine triphosphatase was obtained from skeletal muscle microsomes by extraction with deoxycholate. The Mg++-moderated soluble microsomal ATPase is activated loto ZO-fold by 10m5 M Gaff and inhibited by ethylene glycol bis(P-aminoethyl ether)tetraacetate. Spontaneous formation of microsomal vesicles from solubilized microsomes occurs on removal of deoxycholate by dilution with water or Sephadex chromatography. The soluble ATPase preparations contain phospholipids in amounts comparable to the intact microsomes and treatment with phospholipase C causes an inhibition of the ATPase activity. The inhibition of ATPase activity and Ca++ transport of regenerated microsomes by phospholipase C can be reversed with the addition of synthetic lecithin and lysolecithin. Electrophoretic separation of solubilized microsomal components causes reversible inactivation of ATPase. Trypsin treatment causes the rapid release of proteins from microsomes accompanied by decreased turbidity and an activation of ATPase activity.