Conformational change in the binding site. (a) Ser207(Oγ)-Asp113(Cγ) distance profiles for the loop (red) and clipped (green) models. Blue and purple lines bracket the experimentally determined critical range in active states . (b) Conformations representing the open and closed forms of the binding site in loop model. (c, d) The correlations between TM6 shift and Ser207-Asp113 distance for the loop and clipped models, respectively.