Figure 2

Distinction between similar and dissimilar function. We regard hydrolase activity, acting on ester bonds and oleoyl-[acyl-carrier protein] hydrolase activity, as similar functions, because their lowest common ancestor, hydrolase activity, acting on ester bonds, is not the root node of the molecular function DAG. However, we would regard hydrolase activity, acting on ester bonds and acyl carrier activity, as dissimilar functions, because their lowest common ancestor is the root node of the DAG. The Figure also illustrates the idea of the distal GO IDs that we extract from an annotation set, in this case describing proteins in the Acyl_ACP thioesterase family. Both acyl carrier activity and oleoyl-[acyl-carrier protein] hydrolase activity have no child nodes within the GO molecular function DAG. These annotations are therefore as specific as possible within the GO function classification. That is, they are distal both within the annotations of this family of proteins and in the overall GO DAG itself. The third GO ID, hydrolase activity, acting on ester bonds, annotates some proteins that are not annotated with the more precise function oleoyl-[acyl-carrier protein] hydrolase activity. For such proteins, hydrolase activity, acting on ester bonds is a distal GO ID.