Average SS Relof GO term pairs for moonlighting proteins. Average SS Rel of GO pairs within function 1, function 2, and pairs from function 1 and 2 were computed separately. (A) Moonlighting proteins in the MPR1 set. Protein 24 is presenilin in Physcomitrella patens (Uniprot ID: A9S846). This protein have one GO term each in F1 and F2 (F1 term GO:0004190, “aspartic type endopeptidase activity” and F2 term GO:0016021, “intergral to membrane”). The two GO terms are in different ontologies, MF and CC respectively, and thus the scores are zero for F1 and F2 (because there is only one term) as well as F1-F2 (because similarity of GO terms in different categories cannot be considered). (B) the MPR2 set; and (C) the MPR3 set.