Fig. 5.

A comparison of the orientations of epibatidine (yellow, displayed as a ball-and-stick model) in the different binding sites of 2BYQ and 3SQ6, showing the accessibility of different regions of the ligand. A, B. The surface of the protein has been hidden in panel A to show the location of epibatidine in the binding site, relative to binding loops B and C. The orientation shown in panel B is the same as that in panel A, but with the protein surface visible. This is the only orientation found in all ten binding sites from 3SQ6 and the C-4′ position is most accessible. C. Accessibility of the C-5′ position is seen in 2BYQ where it is found in four of the five binding sites. D. In 2BYQ, one of the binding poses (chains B & A) also exposes the N-1′ position. The atom numbering used in this figure can be seen in Fig. 1. Potential hydrogen bonds are indicated by yellow dashes. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)