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A subset of GAF domains are evolutionarily conserved sodium sensors
Author(s) -
Cann Martin
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.05669.x
Subject(s) - biology , microbiology and biotechnology , function (biology) , sodium , mutant , biochemistry , gene , chemistry , organic chemistry
Summary 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. Δ cyaB1 and Δ cyaB2 mutant strains did not grow below 0.6 mM Na + and Δ cyaB1 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.