Understanding the lethality of low degree essential proteins

Centrality-lethality rule demonstrates proteins with high degree in the protein-protein interaction (PPI) networks are more likely to be essential than those selected randomly. But why proteins with low degree also have lethality? The differences between low and high degree essential proteins were compared in six centrality measures, the relationship with protein complexes, clustering coefficient, and functional modularity. The results show that there are several properties, such as higher eigenvector centrality, more likely appear in protein complexes, higher clustering coefficient, and more neighbors with the same function, are distinguishable significant between the low and high degree essential proteins.