  Recently, the structural controllability theory has been introduced to
analyze the Protein-Protein Interaction (PPI) network. The indispensable nodes,
which their removal increase the number of driver nodes to control the network,
are found essential in PPI network. However, the PPI network is far from
complete and there may exist many false-positive or false-negative
interactions, which promotes us to question: are these indispensable nodes
robust to structural change? Here we systematically investigate the robustness
of indispensable nodes of PPI network by removing and adding possible
interactions. We found that the indispensable nodes are sensitive to the
structural change and very few edges can change the type of many indispensable
nodes. The finding may promote our understanding to the control principle of
PPI network.
