  Protein-protein interactions can be properly modeled as scale-free complex
networks, while the lethality of proteins has been correlated with the node
degrees, therefore defining a lethality-centrality rule. In this work we
revisit this relevant problem by focusing attention not on proteins as a whole,
but on their functional domains, which are ultimately responsible for their
binding potential. Four networks are considered: the original protein-protein
interaction network, its randomized version, and two domain networks assuming
different lethality hypotheses. By using formal statistical analysis, we show
that the correlation between connectivity and essentiality is higher for
domains than for proteins.
