In Fig 1D the very first equation signifies basal expression, whilst the 2nd implies cooperative self-activation with S the substrate (e.g. nucleotides for mRNA and amino acids for protein production)
The chemical reactions for the self-activating gene and the phosphorylation-dephosphorylation cycle with their price constants are shown in Figs 1D and 1E, respectively.In Fig 1E, the substrate is presented by…