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Model of helices IV and V in lac permease. Helices IV and V are represented as light blue ribbons. The charge pair (Glu-126 and Arg-144; dark blue), as well as the relevant Gly (G115, G121, G141, G147, and G150; red) and Ala (A120, A122, A124, and A127; yellow) residues are indicated.
