Figure 4

Four significant motifs involving interactions between aromatic rings. Ligand molecules are shown as line model and protein side-chains as stick model. The green lines show the connectivities (edges) of the motifs, which, in these examples, are a 2 (ligand atoms) interacting with 3 (protein atoms) fully connected motif. (a) (NRA, NRA) interacting with (CRN, CRN, CRP): 2 ligand atoms interacting with 3 protein atoms located on 3 different aromatic residues; (b) (NRA, NRA) interacting with (CRN, CRP, NRE): 3 protein atoms located on 2 aromatic residues and the aromatic ring of histidine is parallel to that of adenine in the ligand; (c) (CRN, ORA) interacting with (CRN, CRN, CRN): all 3 protein atoms located on 1 residue, tyrosine; (d) (CRN, CRN) interacting with (CRN, CRN, CRN): this motif is the most prevalent motif (in number) and is ranked 22^nd (by significance grade) in Table 4.