Overview of models and model extensions used to derive the final, quantitative model. Starting with the initial Model 1, the quantitative (final) Model 6 was derived step by step keeping the model structure as simple as possible. Models were extended by additional mechanisms/features (see box of each model) to predict finally all of the experimental observations (see legend at the lower right corner). Experimental observations that a model can predict are indicated by the color coded checkmarks ✓. Further properties of the models and the rate equations are given in the Text and in the simulation scripts (Additional file 3).