Lipid dependence of diacylglycerol kinase from Escherichia coli

Diacylglycerol kinase apoprotein was purified from membranes of Escherichia coli K 12. The protein was catalytically inactive, but regained activity upon recombination with phospholipids, certain neutral lipids, or fatty acids. Activation proceeded with positive cooperativity and was independent of the exact chemical structure, bilayer arrangement or electrical charge of the lipid. The apoprotein was activated by lysophosphatidylethanolamine but not by lysophosphatidylcholine. 1-Monooleoylglycerol was an effective activator and substrate at the same time. The fluidity and the polarity of lipids appeared to be generally important for activation. Lipid polarity was estimated by a triacylglycerol/phosphatidylcholine-partitioning procedure. All lipids showing preferential association with triacylglycerol failed to activate the kinase apoprotein even in the presence of detergent. It is concluded that a defined hydrophilic/lipophilic balance of the lipid was required for the formation of a functional lipoprotein complex.