Table 2. Main statistics of PPI networks.

	Proteins	Interactions	Avg degree
Saccharomyces cerevisiae (yeast)
Collins	1,622	9,074	5.59
Krogan core	2,708	7,123	2.63
Krogan extended	3,672	14,317	3.89
Gavin	1,855	7,669	4.13
DIP-yeast	4,638	21,377	4.60
Biogrid yeast	6,436	229,409	35.64
Homo sapiens (human)
HPRD	9,453	36,867	3.90
Biogrid human	17,545	233,688	13.31