Crosslinking studies on the Ca2+, Mg2+-activated ATPase of Escherichia coli.

Crosslinking of membrane proteins of Escherichia coli with dithiobis (succinimidyl propionate) (DSP) resulted in loss of several enzyme activities including the Ca2+, Mg2+-activated ATPase. This enzyme was crosslinked by DSP to the membrane and was not released by dialysis at low ionic strength in the absence of dithiothreitol which could cleave the crosslinking group. DSP inactivated both phosphohydrolase and coupling activities of the solubilized ATPase. Loss of hydrolytic activity could be correlated with the extent of reaction of the alpha and/or beta subunits of the enzyme. The loss of coupling activity appeared to be associated with modification of the gamma and/or delta subunits.