CcbP is a Ca(2+) binding protein which, in Anabaena, is thought to bind Ca(2+) by protein surface charge. When bound to Ca(2+), the protein becomes more compact and the level of free calcium decreases. The free Ca(2+) concentration which is regulated by CcbP is critical for the differentiation process [1]. Calcium signalling is widespread in bacterial species, and prokaryotic cells like eukaryotes are equipped with all the elements to maintain Ca2+ homeostasis [2].

1: CcbP, a calcium-binding protein from Anabaena sp. PCC 7120, provides evidence that calcium ions regulate heterocyst differentiation. Zhao Y, Shi Y, Zhao W, Huang X, Wang D, Brown N, Brand J, Zhao J; Proc Natl Acad Sci U S A. 2005;102:5744-5748. PMID:15811937

2: Calcium signalling in bacteria. Dominguez DC; Mol Microbiol. 2004;54:291-297. PMID:15469503