Figure 2.

A surface model of the mouth of the active-site cavity is shown in (a) as modelled in chain D, where His762 could be modelled, and in (b) with His762 removed from the structure. Phe173 is on the opposite side of the opening and effectively delimits the active-site channel opening with His762. The residues forming the active-site cavity are shown in cyan (chain D) and magenta (chain C). TPQ471 and the proposed active-site gate residue Leu469 can be seen at the bottom of the funnel, as well as the active-site copper, which is depicted as a sphere.