FIGURE 2.

Schematic diagram illustrating species within “non-receptor-coupling” and “receptor-coupling” models. Base model interactions show the ligand (i), receptor (R), ligand-receptor complex (C), unbound (P) and ligand bound (G) unique HSPG site, ternary complex (T), and ligand-receptor dimers (C₂) with one (X) and two (T₂) unique HSPG sites which are common to both models. Identical sets are included for each ligand i. In the “Non-receptor-coupling” model, the common HSPG sites (P^c) bind ligand (G^c) but do not interact with receptors. In the “receptor-coupling” model, the common HSPG (P^c) bind ligand (G^c) and form higher order complexes with receptors (T^c, X^c, ${\mathrm{T}}_2^{\mathrm{C}}$, ${\mathrm{T}}_{\mathrm{jj}}^{\mathrm{c}}$). Specific reactions are shown in Table 1.