Direct Ab-initio Molecular Dynamics (AIMD) Study on the Radiation Effects on Catalytic Triad composed of Ser-His-Glu residues

High energy irradiation to the hydrogen bonded system is important in relevance with the initial process of DNA and enzyme damages. In the present study, the effects of radiation to catalytic triad have been investigated by means of direct ab-initio molecular dynamics (AIMD) calculation. As a model of the catalytic triad, Ser-His-Glu residue, which is one of the important enzymes in the acylation reaction, was examined. The ionization and electron attachment processes in Ser-His-Glu were investigated as the radiation effects,. The direct AIMD calculation showed that a proton of His is spontaneously transferred to carbonyl oxygen of Glu after the ionization. However, the whole structure of catalytic triad was essentially kept after the ionization. On the other hand, in the case of the electron capture in the model catalytic triad Ser-His-Glu, the dissociation of Glu residue from [Ser-His] was found as a product channel. The mechanism of ionization and electron capture process in the catalytic triad was discussed on the basis of theoretical results.