What must the membrane protein do so that hydrogen ions can flow through it?

To allow hydrogen ions to flow through a membrane protein, the protein must form a channel or pore that selectively permits the passage of these ions. This often involves conformational changes in the protein structure that create a pathway through the lipid bilayer. Additionally, the protein may utilize mechanisms like facilitated diffusion or active transport, depending on the concentration gradient and energy requirements. Proper orientation and charge properties of the protein's interior are also crucial for the selective transport of hydrogen ions.