Figure 2.

Network motifs and evolutionary motif modes. There are two interconnected patterns for 3-motifs and six for 4-motifs. Evolutionary motif modes of a 3-motif and a 4-motif of specific topology are shown, different node colors indicating different protein age classes. For example, for each 4-motif of specific topology, in total there are five possible evolutionary motif modes which are marked as #4, #3-1, #2-2, #2-1-1 and #1-1-1-1. The label for an evolutionary motif mode indicates the number of nodes of different age classes within the motif mode. For example, #4 indicates that all the four proteins within the motif mode are of the same age class, and #2-2 indicates that two of the four proteins within the motif mode are of one age class, while the other two are of another age class.