| Abstract: | The diversity of cellular membrane structures associated with regulation of intracellular calcium level is described in several different groups of organisms and cells. All the instances reported refer to cellular processes related to movement, in which calcium ion acts as trigger and/or modulator. In addition, a simplified five-stage picture of the underlying view of evolution of these structures is presented. In short: the choice made by nature in using calcium as intracellular messenger was very early in the history of life; all cellular structures devoted to intracellular calcium regulation, from the simplest form of amoeba to the highly sophisticated apparatus of mammalian skeletal muscle, can be linked together in the chain of evolution. Because the evidence is still sparse, any conclusion more positive would be speculative and of little value. Hopefully, in the coming years, with a better understanding of membrane architecture as a whole and its protein components (i.e. calcium channels, calcium-binding proteins), we will be able to test the first segments of this evolutionary hypothesis. |
