Fig. 6. Binding of Ala-Ala-Ala proceeds via N-terminal engagement followed by C-terminal engagement.

(A) Free energy calculations show that N-terminal engagement followed by C-terminal engagement is more energetically favorable. (B) The N terminus of Ala-Ala-Ala initially interacts with Asp³¹⁷ before transferring to Glu⁶²² and is further coordinated by Asn¹⁹² and Asn³⁴⁸. (C). Once the N terminus has formed a stable interaction, the C terminus engages with Arg⁵⁷ from Lys⁶⁴ and the movement is smoothened by Tyr⁶⁰, Tyr⁶¹, and Tyr⁶⁴ (D).