Calcium Signaling: Up, Down, Up, Down.... What's the Point?

Many cells respond to external signals by generating pulses of the calcium ion in their cytoplasm, which somehow tells other cellular components to turn on or off. In his commentary, Putney poses this decoding problem and explains how a [report][1] by De Koninck and Schulman in this issue shows that one of calcium's main targets, the enzyme calcium-calmodulin, has intrinsic properties that allow it to translate the pulses into useful information for the cell. [1]: http://www.sciencemag.org/cgi/content/short/279/5348/227