  Cyclic adenosine monophosphate (cAMP) is considered a model system for signal
transduction, the mechanism by which cells exchange chemical messages. Our
previous work calculated the Shannon capacity of a single cAMP receptor;
however, a typical cell may have thousands of receptors operating in parallel.
In this paper, we calculate the capacity of a cAMP signal transduction system
with an arbitrary number of independent, indistinguishable receptors. By
leveraging prior results on feedback capacity for a single receptor, we show
(somewhat unexpectedly) that the capacity is achieved by an IID input
distribution, and that the capacity for n receptors is n times the capacity for
a single receptor.
