Before revision:  Here, the signaling proteins are activated by receptors  and these activated signaling proteins activate target proteins , causing that to unbind from the membrane . We found that the signal flow of the system, defined as the activation rate of target protein, shows the following non-trivial variations against the change in the volume fraction of molecules or the affinity of the target protein to the membrane.
After revision:  Here, the signaling proteins are activated by receptors and these activated signaling proteins activate target proteins , causing that to unbind from the membrane if activated. If the target proteins bind frequently, the volume fraction of molecules or the affinity of the target protein to the membrane.