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A subset of GAF domains are evolutionarily conserved sodium sensors.

Cann, M. (2007) 'A subset of GAF domains are evolutionarily conserved sodium sensors.', Molecular microbiology., 64 (2). pp. 461-472.


Most organisms maintain a transmembrane sodium gradient for cell function. Despite the importance of Na+ in physiology, no directly Na+-responsive signalling molecules are known. The CyaB1 and CyaB2 adenylyl cyclases of the cyanobacterium Anabaena PCC 7120 are inhibited by Na+. A D360A mutation in the GAF-B domain of CyaB1 ablated cAMP-mediated autoregulation and Na+ inhibition. Na+ bound the isolated GAF domains of CyaB2. cAMP blocked Na+ binding to GAF domains but Na+ had no effect on cAMP binding. Na+ altered GAF domain structure indicating a mechanism of inhibition independent of cAMP binding. ΔcyaB1 and ΔcyaB2 mutant strains did not grow below 0.6 mM Na+ and ΔcyaB1 cells possessed defects in Na+/H+ antiporter function. Replacement of the CyaB1 GAF domains with those of rat phosphodiesterase type 2 revealed that Na+ inhibition has been conserved since the eukaryotic/bacterial divergence. CyaB1 and CyaB2 are the first identified directly Na+-responsive signalling molecules that function in sodium homeostasis and we propose a subset of GAF domains underpin an evolutionarily conserved Na+ signalling mechanism.

Item Type:Article
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Publisher statement:This is the accepted version of the following article: Cann, M. (2007), A subset of GAF domains are evolutionarily conserved sodium sensors. Molecular Microbiology, 64 (2): 461-472, which has been published in final form at This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.
Record Created:17 Jan 2008
Last Modified:27 Nov 2014 12:13

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