SCOP superfamily partners. The plots show the number of different SCOP superfamilies that are found together in the same sequence with a given superfamily, including the superfamily itself and irrespective of the order or sequence space between domains. This implies that at least two domains have to be identified in a sequence. Superfamily partners for the 10 most abundant superfamilies in human (A), in yeast (B) and bacteria (C) are plotted. Only those superfamilies not found within the first 10 ranks in human are shown inB (P-loop, protein kinase-like, tetratricopeptide repeat, and the classic zinc finger) and C (P-loop rank one in bacteria).