The Lactose Permease in Escherichia Coli Is an H⁺-Lactose Symporter

Multiple Choice

The lactose permease in Escherichia coli is an H⁺-lactose symporter that mediates the inward active transport of lactose if this sugar is present in the environment instead of glucose. Which of the following is true about this transporter?

A) It has a twofold pseudosymmetrical structure.
B) Lactose and H⁺ bind to two different conformations of the transporter.
C) The transporter goes through an intermediate state in which the bound lactose is open to both sides of the membrane.
D) If lactose and H⁺ concentrations are changed sufficiently, the transporter can act as an H⁺-lactose antiporter.
E) All of the above.