[Mg2+ cation initiates the conversion of nucleoside triphosphate to nucleoside monophospate through a radical...

DFT:B3LYP (6-311G** basis set) quantum molecular dynamics simulation was used to study the conversion of guanosine triphosphate (GTP) to guanosine monophosphate upon the action of Mg2+. The computations were carried out at 310 K in a basin of 178 water molecules surrounding a Mg(2+)-GTP complex and imitating the behavior of the solvent. The cleavage of the Mg(2+)-GTP complex occurs over the 5-ps period and gives rise to two inorganic phosphates (Pi), a hydrated Mg2+ complex, atomic oxygen, and highly reactive GMP radical. The appearance of this radical is a result of action of the Mg2+ cation, which initiates the radical mechanism of GTP cleavage. At the very early step of interaction with GTP, Mg2+ is reduced to Mg+, thus producing an ion radical pair (+)Mg-GTP(3-). In the absence of Mg2+, a non-reactive form of GMP is formed rather than GMP; the process corresponds to hydrolytic cleavage of GTP through the ionic mechanism. The formation of GMP and its analogues with adenosine, cytidine, thymidine, and uridine is, seemingly, a key point in DNA and RNA synthesis.