Naturally-Occurring Fusion Between the Regulatory and Catalytic Components of Type IIP Restriction-Modification Systems
Jixiao Liang · OhioLink ETD Center (Ohio Library and Information Network) · 2013
Restriction-modification (R-M) systems play key roles in controlling gene flow among bacteria and archaea, and their own genetic mobility depends critically on their regulation, but the regulation of these systems is poorly understood.The PvuII R-M system is a Type IIP R-M system in that the protective DNA methyltransferase (MTase) is a separate and independently-active protein from the potentially lethal restriction endonuclease (REase).PvuII is one of the best studied of the R-M systems that use a positive feedback regulatory loop, involving a transcriptional regulator called C protein, to delay expression of the REase relative to that of the MTase.This allows protective methylation of a new host cell's DNA before the REase is produced.In searching for R-M systems related to PvuII, in order to study evolution and variation of its regulatory system, a putative system was found in the genome sequence of the bacterium Niabella soli strain DSM 19437, in which the regulatory C protein and the REase are translationally fused.The hypothesis is that N. soli truly produces a fused C-R protein, and that it is active as both a REase and as an autogenous regulator.The genes for the N. soli R-M system were synthesized, produced and purified with affinity tags, and the