Figure 7. Channeling model of cGMP turnover.

1. cGMP molecules synthesized by the GC receptor rapidly bind to the CNGK channel. CNGK, PDE5, and cGMP form a ternary complex, and cGMP bound to CNGK is subsequently transferred to PDE5 for hydrolysis without being released to the cytosol.
2. Relationship between cGMP synthesis rate and free cGMP concentration. We assume that a single GC molecule can synthesize 10 cGMP molecules during its lifetime of 150 ms (Pichlo et al, 2014). Inset: expanded scale.