Evolutionary conservation of domain-domain interactions

Table 1 DDI-PPI mapping: all protein interactions

Organism^a	E. coli	yeast	worm	fly	human
Number of PPIs^b	6,934	24,699	5,315	24,703	28,800
Number of PPIs with known domains^c (N)	6,038	18,202	3,351	14,939	25,004
Number of PPIs to which DDIs could be mapped^d (n) (%; n/N*100) Median value of random networks (P value)	806 (13%) 295 (<0.001)	1,660 (9%) 363 (<0.001)	375 (11%) 142 (<0.001)	891 (6%) 276 (<0.001)	4,924 (20%) 911 (<0.001)
No. of PPIs to which DDIs could be mapped, disregarding PPI-DDI mappings due to overlap between the structural database and the PPI data (n)(%; n/N*100) Median value of random networks (P value)	755 (13%) 288 (<0.001)	1608 (9%) 353 (<0.001)	375 (11%) 142 (<0.001)	889 (6%) 276 (<0.001)	3,989 (16%) 856 (<0.001)

^aOrganism labeling: yeast, S. cerevisiae; worm, C. elegans; fly, D. melanogaster. ^bSee Figure 1a. ^cSee Figure 1c. ^dSee Figure 1e. DDI, domain-domain interaction; PPI, protein-protein interaction.

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