Fig. 5

Hierarchical transition graphs (HTGs) of Model 1. Each node is labelled with a set of letters denoting the type of the node, followed by the number of states that node is representing. For states having the same type and number of states, a number in parentheses is added to the name to differentiate them. The size of the node represents the number of states contained within the node. The irreversible components (‘i#’) represent states which do not contain any cycles or homoeostatic behaviours. The strongly connected components (‘ct#’ and ‘ca#’) represent cyclic or homoeostatic behaviours. The deadlocked state (‘ss-’) represents a single state where the system dynamics seize to function. The nodes and edges in cyan represent the nodes and edges which are conserved in all four models of PDK regulation. The HTGs of the remaining models 2, 3 and 4 are provided as Additional file 7