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Lookup NU author(s): Dr Michael Gray
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Carbon dioxide is fundamental to the physiology of all organisms. There is considerable interest in the precise molecular mechanisms that organisms use to directly sense CO2. Here we demonstrate that a mammalian recombinant G-protein-activated adenylyl cyclase and the related Rv1625c adenylyl cyclase of Mycobacterium tuberculosis are specifically stimulated by CO2. Stimulation occurred at physiological concentrations of CO2 through increased kcat.CO2 increased the affinity of enzyme for metal co-factor, but contact with metal was not necessary as CO2 interacted directly with apoenzyme. CO2 stimulated the activity of both G-protein-regulated adenylyl cyclases and Rv1625c in vivo. Activation of G-protein regulated adenylyl cyclases by CO2 gave a corresponding increase in cAMP-response element-binding protein ( CREB) phosphorylation. Comparison of the responses of the G-protein regulated adenylyl cyclases and the molecularly, and biochemically distinct mammalian soluble adenylyl cyclase revealed that whereas G-protein- regulated enzymes are responsive to CO2, the soluble adenylyl cyclase is responsive to both CO2 and bicarbonate ion. We have, thus, identified a signaling enzyme by which eukaryotes can directly detect and respond to fluctuating CO2.
Author(s): Townsend PD, Holliday PM, Fenyk S, Hess KC, Gray MA, Hodgson DRW, Cann MJ
Publication type: Article
Publication status: Published
Journal: Journal of Biological Chemistry
Year: 2009
Volume: 284
Issue: 2
Pages: 784-791
ISSN (print): 0021-9258
ISSN (electronic): 1083-351X
Publisher: American Society for Biochemistry and Molecular Biology, Inc.
URL: http://dx.doi.org/10.1074/jbc.M807239200
DOI: 10.1074/jbc.M807239200
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