sentence: The two-step process was described by the curvilinear pathway followed by the excess proton , providing a single continuous CV that was sampled to collect a continuous PMF for this process.Our calculations of the PT PMFs and the rate constants with either Cl present or absent suggest that a ( perhaps the ) key mechanism of Cl / H coupling in ClC-ec1 is that Cl significantly facilitates the deprotonation of E148 .