Effect of divalent cations on the ATPase activity of Escherichia coli SecA

It was found that Ca2+ stimulates the intrinsic SecA ATPase activity in the absence as well as in the presence of liposome, On the other hand, Mg2+, the general cofactor for ATPase. did not affect the intrinsic SecA ATPase but reduced the portion of ATPase activity enhanced by. Ca2+. The enhancement of SecA ATPase activity correlated well with the increase in 8-anilino-1-naphthalene-sulfonic acid binding of SecA, suggesting that increased exposure of hydrophobic residues stimulates the enzyme activity. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.