Carbonic anhydrase hydrogen bond network

Kiefer, L. L., Paterno, S. A., and Fierke, C. A., Hydrogen bond network in the metal binding site of carbonic anhydrase enhances zinc affinity and catalytic efficiency, J. Am. Chem. Soc. 117, 6831-6837 (1995). 

Figure 14 X-ray diffraction (XRD) structures of the first dicationic Zn-aqua (a) and Zn-heptylamine (b) complexes. Hydrogen bond networks in the cahxarene-based aqua complex (c) and in carbonic anhydrase (d). Distances are given in angstrom. ...

The most ordered surface waters are those around charged side chains or in surface crevices. Occasionally those crevices can be very deep, such as the active site pocket in carbonic anhydrase, which extends about 15 A in from the surface, with a network of water molecules (Lindskog f al., 1971). The well-ordered waters at the protein surface are usually part of an approximately tetrahedral (but sometimes planar trigonal) network of hydrogen bonds to the protein and to other waters. An example from rubredoxin is shown in Fig. 60. 

---