Computational Analysis of Electron Tunneling Pathways of Blue-Light Photoreceptors

Abstract

DNA phtolyases and cryptochrome DASH (cry-DASH) enzymes in the blue-light photoreceptor family repair UV-damaged DNA by photo-induced electron transfer reaction. Recently (Miyazawa et al., 2008) we analyzed the electron tunneling pathways in a class I CPD photolyase derived from A. nidulans and identified a key residue, Met-353, which is perfectly conserved in the class I CPD photolyases. Interestingly, this site is switched to histidine in 6-4 photolyases, and to glutamine in cry-DASH enzymes. For instance, Met-353 is replaced to Gln-395 in cry-DASH. It is likely that the amino acid residue at the site controls the enzymatic functions of the blue-light photoreceptor family. Until now, the electron transfer pathways in cry-DASH enzymes remain unclear, while those of CPD photolyases are studied well.To characterize the roles of the amino acid residue at the site, we performed molecular dynamics simulation and electronic state calculations of the CPD photolyase of A. nidulans and the cry-DASH. We analyzed the electron tunneling pathways in the forward and backward electron transfer reactions between FADH- and CPD of these two enzymes. As a result, we observed busy trafficking of electron-tunneling current at both Met-353 of the CPD photolyase and Gln-395 of the cry-DASH.