GTP and ATP are similar structures with the adenosine and guanosine groups differing. Both are involved in a vast array of biological functions.
However it has been shown that in certain cases, GTP and water can mimic ATP (Niefind et al., 1999).
Are there examples where ATP has acted as a mimetic of GTP? Or in other words, are there any proteins that can't discriminate between GTP and ATP very well?