Involvement of a periplasmic protein kinase in DNA strand break repair and homologous recombination in Escherichia coli

Abstract

The involvement of signal transduction in the repair of radiation-induced damage to DNA has been known in eukaryotes but remains understudied in bacteria. This article for the first time demonstrates a role for the periplasmic lipoprotein (YfgL) with protein kinase activity transducing a signal for DNA strand break repair in Escherichia coli. Purified YfgL protein showed physical as well as functional interaction with pyrroloquinoline-quinone in solution; the protein kinase activity of YfgL was strongly stimulated in the presence of pyrroloquinoline-quinone. Transgenic E. coli cells producing Deinococcus radiodurans pyrroloquinoline-quinone synthase showed nearly four log cycle improvement in UVC dark survival, 0-fold increases in gamma radiation resistance as compared with untransformed cells. Pyrroloquinoline-quinone enhanced the UV resistance of E. coli through the YfgL protein; required the active recombination repair proteins. The yfgL mutant showed higher sensitivity to UVC, mitomycin C, gamma radiation as compared with wild-type cells, showed a strong impairment in homologous DNA recombination. The mutant expressing an active YfgL in trans recovered the lost phenotypes to nearly wild-type levels. The results strongly suggest that the periplasmic phosphoquinolipoprotein kinase YfgL plays an important role in radiation-induced DNA strand break repair, homologous recombination in E. coli.