Figure 2.

Distribution of amino acids acting as Zn(II) ligands in structural proteins, enzymes, and agonist-gated receptors. The frequency of zinc ligand amino acids was analyzed in 10,931 sites of 4882 proteins with structural or catalytic activity. The results are expressed separately for each protein regardless of its functions. The data for the structural and catalytic sites in proteins was extracted from Andreini et al. [5], while the data for 14 agonist-gated receptors is further summarized in Table 1. Currently, only one crystalline structure is available for a receptor-gated channel with its allosteric modulator zinc [20].