Figure 4.

Analog-digital coupling involving Ras signaling nanoclusters. (A) Analog signals allow graded responses proportional to input whereas digital or high gain switch-like signaling results in maximal output from a wide range of inputs – amplifying weak inputs into maximum outputs. (B) Ras nanoclusters operate as digital amplifiers. (C) Digital quantal sampling of analog inputs can generate high fidelity analog-like outputs if sampling time (Ras activation/de-activation and nanocluster lifetime) is very fast and sample precision (number of nanoclusters) is high. (D) High fidelity digital Ras nanocluster signaling ensures that the analog extracellular signal is converted into a graded cytosolic signaling response. This Figure is reproduced in color in Molecular Membrane Biology online.