|
Figure 2.
Figure 2 Schematic drawing of interactions and distances around
the active site determined from the crystal structure of BCA II
at pH 7.5. The net charges assigned by theoretical calculations
using MOPAC are shown. The side-chain atom Gln91 O  1
(net charge -0.30) accepts a hydrogen bond from of His93 N  1
(net charge -0.21) and contributes to His93 ligand
stabilization. The side-chain atom of Gln91 N 2,
with a net charge of -0.40, has a dominant role in the binding
of water molecule W482, with net charge of +0.02, in its
slightly acidic or cationic form. This interaction is likely to
be more hydrogen-bonding in character than the interaction
between W162 (net charge +0.01) and His63 N 2
(net charge -0.14) that has been a biological focus in the case
of HCA II. This finding suggests that the dipole donor group of
Gln91 may also participate in processes that require relatively
rapid proton movement or release.
|
