Lactose permease has a structure that consists of two halves, each of which comprises six membrane-spanning alpha helices.
The two halves are well separated and are joined by a single stretch of polypeptide. The sugar lies in a pocket in the center of the protein and is accessible from a path that leads from the interior of the cell.
The X-ray crystal structure was solved in 2003 by J. Abramson.
Lactose permease can be classified as a symporter, which uses the gradient of H+ towards the cell to transfer lactose along into the cell.