title: Why Calcium? How Calcium Became the Best Communicator.
abstract: Calcium carries messages to virtually all important functions of cells. Although it was already active in unicellular organisms, its role became universally important after the transition to multicellular life. In this Minireview, we explore how calcium ended up in this privileged position. Most likely its unique coordination chemistry was a decisive factor as it makes its binding by complex molecules particularly easy even in the presence of large excesses of other cations, e.g. magnesium. Its free concentration within cells can thus be maintained at the very low levels demanded by the signaling function. A large cadre of proteins has evolved to bind or transport calcium. They all contribute to buffer it within cells, but a number of them also decode its message for the benefit of the target. The most important of these "calcium sensors" are the EF-hand proteins. Calcium is an ambivalent messenger. Although essential to the correct functioning of cell processes, if not carefully controlled spatially and temporally within cells, it generates variously severe cell dysfunctions, and even cell death.
authors.affiliation: From the Venetian Institute of Molecular Medicine, University of Padova, 35131 Padova, Italy and ernesto.carafoli@unipd.it.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Carafoli
authors.affiliation: the Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry, 37077 Goettingen, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Krebs
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; D002118:Calcium
keywords: calcium; calcium ATPase; calcium channel; calcium signal; calcium transport; calcium-binding protein; calmodulin; magnesium