I was studying about G-protein coupled signaling sysytem, somewhere they have mentioned about need of Mg$^{2+}$ for acticty of G-protein and related it to increase of cyclic AMP production. On further reading I came to know that the said ion is related to GTPase activity of G-protein, but how does it relate to incresed cyclic AMP production?

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    $\begingroup$ Welcome to SE Biology. Please take the Tour and read about asking questions here. You will find that you are expected to do some research before posting. Search for “role of magnesium ions in enzyme reactions” to find the answer to this basic biochemistry question. (And please pay attention to capitalisation.) $\endgroup$ – David May 7 '19 at 17:59
  • $\begingroup$ You will find the basic answer in my response to a question on the role of magnesium in ATP reactions. The situation for GTP is the same. It has nothing specific to do with G proteins. $\endgroup$ – David May 10 '19 at 15:12

Ion can change secondary structure of an enzyme. Magnesium ion is coordinated within certain domains (for example, EF-hand motif) and makes them more ordered. Usually it happens via hydrophilic shell of residues embedded into a hydrophobic one (https://www.pnas.org/content/87/15/5648).

You can reverse it by adding a chelator (EDTA, for example) and protein is more disordered which can affect it's activity.


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