Avidity model predicts a bimodal distribution of PPDK subunit phosphorylation states. Subunit state configurations were evaluated using a model of spatial arrangements of PPDK subunits. Presented is the steady-state fraction (see Methods) of each configuration of the PPDK tetramer. We focused only on configurations of either PPDK1 (marked in white) or PPDK2 (marked in black) subunits. Similar results hold for configurations where one or more subunits are in the PPDK0 state (see additional file 2). Model parameters are: Vp = Vk = 0.2 [koff1], kon2 = 200 [koff2] and total PPDK/total RP = 100 [11, 13, 33].