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Figure 6
The motions of Tyr48 and Tyr137 are coupled, mediated by Ile52. (a) The five major clusters of the tyrosine gate are shown extracted from the MD trajectories of ligand-free WT FimH (left). Clusters featuring similar structures were extracted from the 150 ns simulations and plotted against their population occurrence (in %). Only the five most abundant clusters, together counting for more than 80% of all possible conformations, are shown. For the cluster with the highest occurrence, the interactions between the two tyrosine residues and all other protein residues are also shown (right). (b) Probability of having the centre of mass of the side chain of Ile52 at a certain distance from the centre of mass of the Tyr48 and the Tyr137 side chain at the same time. The probabilities are shown for the ligand-free simulations of the WT (left), the Y48A mutant (middle) and the Y137A mutant (right). In the WT Tyr48 and Tyr137 show a clear preference for being close to Ile52 (a distance of the two centres of mass of <6 Å), indicating an Ile52-mediated coupling of the motion in the tyrosine gate. This connection is weakened (Y48A) or lost (Y137A) following mutation of these residues.

IUCrJ
Volume 4| Part 1| January 2017| Pages 7-23
ISSN: 2052-2525
https://doi.org/10.1107/S2052252516016675