Figure 5.

Tree diagrams of the first-level GPCR clusters, showing member sequences of cluster Pe001, which has a conservative core (A); and member sequences of cluster Ol001, which has no conservative core (B). In (A), the 3D protein structure of P51681 is displayed in its node, and a line segment is used to represent a zero-distance edge connecting two nodes in the core. In (B), a double-headed arrow is used to represent the shortest edge connecting two nodes in the core, and a single-headed arrow (directed toward the node closer to the core) is used to represent all other edges connecting two nodes in the cluster. Each edge is labeled with its length.