(A) Left panel, surface representation of the AliD:permease complex predicted by AF. Each protein is color-coded and labeled accordingly. CH: coupling helix. (B) Different configurations of the NBDs in the inward (closed, upper panel) and outward (open, lower panel) conformations. AmiF and AmiD are represented in cartoon form, and the ATP molecules are shown as spheres. (C) View corresponding to a slice located at the blue plane depicted in A, right panel. The upper panel highlights the identified hydrophobic residues that obstruct the channel in the inward, closed conformation. In contrast, the lower panel shows the location of the same residues in the outward, open conformation. The generated cavity, presumably allowing oligopeptide transport, is marked in blue and outlined with a dashed black line. Relevant residues are labeled and represented as spheres. (D) Different proteins of the Ami system and conceptual schematic model for the mechanism of oligopeptide transport.

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