Phosphatidylglycerol Directs Binding and Inhibitory Action of EIIAGlc Protein on the Maltose Transporter

The signal-transducing protein EIIA Glc belongs to the phosphoenolpyruvate carbohydrate phosphotransferase system. In its dephosphorylated state, EIIA Glc is a negative regulator for several permeases, including the maltose transporter MalFGK 2 . How EIIA Glc is targeted to the membrane, how it interacts with the transporter, and how it inhibits sugar uptake remain obscure. We show here that acidic phospholipids together with the N-terminal tail of EIIA Glc are essential for the high affinity binding of the protein to the transporter. Using protein docking prediction and chemical cross-linking, we demonstrate that EIIA Glc binds to the MalK dimer, interacting with both the nucleotide-binding and the C-terminal regulatory domains. Dissection of the ATPase cycle reveals that EIIA Glc does not affect the binding of ATP but rather inhibits the capacity of MalK to cleave ATP. We propose a mechanism of maltose transport inhibition by this central amphitropic regulatory protein. Background: The protein EIIA Glc inhibits maltose transport. Results: Anionic lipids and N-terminal tail direct the positioning of EIIA Glc onto the MalK dimer to inhibit cleavage of ATP. Conclusion: A mechanism of inhibition of maltose transport by EIIA Glc is presented. Significance: The study highlights the importance of membrane lipids for the correct positioning of EIIA Glc on the transporter.